Magnetic recording medium, production process thereof, and magnetic recording and reproducing apparatus including both oxide and non-oxide perpendicular magnetic layers

ABSTRACT

A magnetic recording medium which is provided on a nonmagnetic substrate  1  with at least an orientation-controlling layer  3  for controlling the orientation of a layer formed directly thereon, a perpendicularly magnetic layer  4  having an easily magnetizing axis oriented mainly perpendicularly relative to the nonmagnetic substrate  1 , and a protective layer  5  and characterized in that the perpendicularly magnetic layer  4  includes two or more magnetic layers, that at least one of the magnetic layers is a layer  4   a  having Co as a main component and containing Pt as well and containing an oxide and that at least another of the magnetic layers is a layer  4   b  having Co as a main component and containing Cr as well and containing no oxide.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is an application filed under 35 U.S.C. § 111(a)claiming the benefit pursuant to 35 U.S.C. §119(e)(1) of the filing dateof Provisional Application No. 60/462,298 filed Apr. 14, 2003 pursuantto 35 U.S.C. §111(b).

TECHNICAL FIELD

This invention relates to a magnetic recording medium which is providedon a nonmagnetic substrate with at least an orientation-controllinglayer for controlling the orientation of a layer formed directlythereon, a perpendicularly magnetic layer having an easily magnetizingaxis oriented mainly perpendicularly relative to the nonmagneticsubstrate, and a protective layer, to a method for the productionthereof and to a magnetic recording and reproducing apparatus.

BACKGROUND ART

The hard disk drive (HDD) that is one kind of the magnetic recording andreproducing apparatus has the recording density thereof growing atpresent at an annual rate of 60% or more. The trend of this growth issaid to last in the future. Thus, the development of a magneticrecording head and the development of a magnetic recording medium thatfit the high recording density are being promoted.

The magnetic recording medium mounted on the magnetic recording andreproducing apparatus currently available in the market is mainly anin-plane magnetic recording medium having the easily magnetizing axis ina magnetic film oriented horizontally relative to the substrate. Theterm “easily magnetizing axis” as used herein refers to the axis thatallows easy orientation of magnetization and, in the case of a Co-basedalloy, refers to the c axis in the hcp structure of Co.

In the in-plane magnetic recording medium of this kind, an addition tothe recording density results in unduly decreasing the volume of amagnetic layer per recording bit and possibly degrading the read/writeproperty due to the effect of thermal fluctuation. Further, during theaugmentation of the recording density, the medium noise tends toincrease under the influence of the diamagnetic field that is generatedin the boundary region between adjacent recording bits.

In contrast, the so-called perpendicularly magnetic recording mediumwhich has the easily magnetizing axis in the magnetic film orientedmainly perpendicularly, even during the augmentation of the recordingmedium, suffers only minutely from the influence of the diamagneticfield in the boundary region between adjacent recording bits and, owingto the formation of bright boundary bits, represses the increase ofnoise. Moreover, it defies the effect of thermal fluctuation because itis capable of repressing the decrease of the volume of recording bitsdue to the augmentation of the recording density. Such being the case,the perpendicularly magnetic recording has been arresting greatattention, and the configurations of a medium fitting theperpendicularly magnetic recording have been proposed in recent years.

In recent years, the feasibility of adopting a single magnetic pole headexcelling in the ability to write on the perpendicularly magnetic layerwith a view to answering the demand for further augmentation of therecording density of the magnetic recording medium has been beingstudied. With the object of materializing this single magnetic polehead, the magnetic recording medium which has improved the efficiency ofexchange of magnetic flux between the single magnetic pole head and themagnetic recording medium by interposing the so-called lining layer,i.e. a layer formed of a soft magnetic material, between theperpendicularly magnetic layer which is a recording layer and thesubstrate has been proposed.

When the magnetic recording medium which is merely provided with thelining layer as described above is used, however, it falls short ofsatisfying the read/write property during the course of reproducing therecord, the property of resisting thermal fluctuation and the recordresolving power. Thus, the desirability of developing a magneticrecording medium that excels in these properties has been findingrecognition.

The reconciliation of the augmentation of the ratio of signal to noise(S/N ratio) during the reproduction, which is particularly important forthe read/write property, with the enhancement of the resistance tothermal fluctuation constitutes an essential matter for the sake of thefuture augmentation of recording density. These two factors have acontradictory relation such that one of them declines unduly when theother is enhanced. The reconciliation of them at a high level poses animportant problem.

As one of the problems which encounter the perpendicularly magneticrecording medium, the fact that the use of a magnetic layer of theCoCrPt system which is common to all recording and reproducing magneticlayers results in rendering difficult the acquisition of a properread/write property because this magnetic layer is deficient insegregation of Cr and insufficient to attain physical separation, finedivision and magnetic isolation of magnetic grains may be cited.

In the meanwhile, the utilization of a material containing an oxide inCoCrPt in the magnetic layer of the in-plane magnetic recording mediumhas been proposed (JP-A 2000-276729, for example).

The magnetic layer of this construction is enabled, by using an oxideinstead of relying on segregation of Cr, to attain sufficient separationof grains to a certain extent even in the perpendicularly magneticmedium.

The medium constructed as described above uses a material that decreasesthe amount of Cr to be added thereto and adds an oxide instead. It,therefore, entails such problems as suffering the coercive force of themagnetic layer to grow excessively and failing to effect thoroughrecording of data with the head because the smallness of the amount ofCr to be added results in increasing the ratio of Pt in the magneticgrains in the magnetic layer and enlarging the constant of magneticanisotropy, Ku, of magnetic grains.

It becomes necessary, therefore, to adopt a method for lowering thecoercive force of the magnetic layer and effecting thorough recording byresorting to such means as decreasing the thickness of the magneticlayer and increasing the amount of Cr to be added. In the meantime, thefact that the decrease of the thickness of the magnetic layer and theincrease of the Cr content result in decreasing the magnetic anisotropyconstant Ku of magnetic grains and degrading the nucleation as wellentails degradation of the property of thermal fluctuation. Further, theact that the output during the reproduction of data diminishes resultsin decreasing the ratio of this output to the system noise inherent inthe recording and reproducing system and possibly disrupting theacquisition of a sufficient reproducing property. As a result, theproperties to be acquired no longer fit the high-density recording.

In the circumstances, the development of a magnetic recording mediumwhich is endowed with an enhanced property of thermal fluctuation, asufficient read/write property for high-density recording, aparticularly proper data recording property, and a high signal/noise(S/N) ratio during the reproduction has been yearned for.

This invention originated in the appreciation of such true state ofaffairs as mentioned above and is aimed at providing a magneticrecording medium which possesses an exalted read/write property and anenhanced property of thermal fluctuation and allows information of highdensity to be recorded and reproduced, a method for the productionthereof, and a magnetic recording and reproducing apparatus.

DISCLOSURE OF THE INVENTION

The present invention provides a magnetic recording medium provided on anonmagnetic substrate with at least an orientation-controlling layer forcontrolling the orientation of a layer formed directly thereon, aperpendicularly magnetic layer having an easily magnetizing axisoriented mainly perpendicularly relative to the nonmagnetic substrate,and a protective layer, the medium being characterized in that theperpendicularly magnetic layer comprises two or more magnetic layers,that at least one of the magnetic layers is a layer having Co as a maincomponent and containing Pt as well and containing an oxide and that atleast another of the magnetic layers is a layer having Co as a maincomponent and containing Cr as well and containing no oxide.

In the magnetic recording medium, the magnetic layer containing theoxide has magnetic crystal grains dispersed therein and the crystalgrains penetrate the layer in columnar forms.

In the magnetic recording medium, the oxide is an oxide of at least onenonmagnetic metal selected from among Cr, Si, Ta, Al and Ti.

In the magnetic recording medium, the oxide is Cr₂O₃ or SiO₂,

In the magnetic recording medium, the magnetic layer containing theoxide has an oxide content of 3 mol % or more and 12 mol % or less.

In the magnetic recording medium, the magnetic layer containing theoxide has Co as a main component and has a Cr content of 0 at % or moreand 16 at % or less and a Pt content of 10 at % or more and 25 at % orless.

In the magnetic recording medium, the magnetic layer containing theoxide contains at least one element selected from the group consistingof B, Ta, Mo, Cu, Nd, W, Nb, Sm, Th, Ru and Re and has a total contentof the at least one element is 8 at % or less.

In the magnetic recording medium, the magnetic layer containing no oxidehas Co as a main component and has a Cr content of 14 at % or more and30 at % or less.

In the magnetic recording medium, the magnetic layer containing no oxidehas Co as a main component and has a Cr content of 14 at % or more and30 at % or less and a Pt content of 8 at % or more and 20 at % or less.

In the magnetic recording medium, the magnetic layer containing no oxidecontains at least one element selected from the group consisting of B,Ta, Mo, Cu, Nd, W, Nb, Sm, Th, Ru and Re and has a total content of theat least one element is 8 at % or less.

In the magnetic recording medium, the perpendicularly magnetic layer hasthe magnetic layer containing no oxide formed on the magnetic layercontaining the oxide.

In the magnetic recording medium, the perpendicularly magnetic layercontains two or more oxide-containing layers.

In the magnetic recording medium, the perpendicularly magnetic layercontains two or more layers containing no oxide.

In the magnetic recording medium, the perpendicularly magnetic layer hasa nonmagnetic layer between the magnetic layers.

In the magnetic recording medium, the perpendicularly magnetic layercomprises a plurality of magnetic layers each constituted of crystalgrains, in which the crystal grains on an upper side are epitaxiallygrown from the crystal grains on a lower side.

In the magnetic recording medium, each of said magnetic layers isconstituted of at least one crystal grain and, during epitaxial growthof the at least one crystal grain constituting an upper magnetic layerfrom the at least one crystal grain constituting a lower magnetic layer,a ratio of the first mentioned at least one crystal grain to the secondmentioned at least one crystal grain corresponds to one to one, one toplurality or plurality to one.

In the magnetic recording medium, the perpendicularly magnetic layer hasa ratio of one to one, one to plurality or plurality to one, which ratiois given to at least one crystal grain of the magnetic layer containingthe oxide and at least one crystal grain of the magnetic layercontaining no oxide, and wherein the at least one crystal grain on anupper side is epitaxially grown from the at least one crystal grain on alower side.

The invention further provides a method for the production of a magneticrecording medium provided on a nonmagnetic substrate with at least anorientation-controlling layer for controlling the orientation of a layerformed directly thereon, a perpendicularly magnetic layer having aneasily magnetizing axis oriented mainly perpendicularly relative to thenonmagnetic substrate, and a protective layer, the method beingcharacterized by forming the perpendicularly magnetic layer of two ormore magnetic layers, wherein at least one of the two or more magneticlayers is a layer having Co as a main component, containing Pt as welland containing an oxide and at least another of the two or more magneticlayers is a layer having Co as a main component, containing Cr as welland containing no oxide.

In the method, the magnetic layer containing the oxide has magneticcrystal grains dispersed therein and the crystal grains penetrate thelayer in columnar forms.

In the method, the magnetic layer containing no oxide is disposed on themagnetic layer containing the oxide.

In the method, the perpendicularly magnetic layer contains two or moreoxide-containing layers.

In the method, the perpendicularly magnetic layer contains two or morelayers containing no oxide

In the method, the perpendicularly magnetic layer is provided betweenthe magnetic layers with a nonmagnetic layer.

In the method, the perpendicularly magnetic layer has a ratio of one toone, one to plurality or plurality to one, which ratio is given to atleast one crystal grain of the magnetic layer containing the oxide andat least one crystal grain of the magnetic layer containing no oxide,and wherein the at least one crystal grain on an upper side isepitaxially grown from the at least one crystal grain on a lower side.

In the method, the perpendicularly magnetic layer is formed using afilm-forming gas to which an oxygen gas is added.

The invention further provides a magnetic recording and reproducingapparatus furnished with a magnetic recording medium and a magnetic headfor recording and reproducing information in the magnetic recordingmedium, the apparatus being characterized in that the magnetic recordingmedium is the magnetic recording medium.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section illustrating the construction of one exampleof the magnetic recording medium contemplated by this invention.

FIG. 2 is a cross section illustrating the construction of aperpendicularly magnetic layer.

FIG. 3 is a diagram illustrating a case in which the magnetic grains donot form a columnar structure in the magnetic layer.

FIG. 4 is a diagram illustrating one example of the MH curve.

FIG. 5 is a diagram illustrating another example of the MH curve.

FIG. 6 is a cross section illustrating the construction of anotherexample of the magnetic recording medium contemplated by this invention.

FIG. 7 is a cross section illustrating the construction of yet anotherexample of the magnetic recording medium contemplated by this invention.

FIG. 8 is a cross section illustrating the construction of still anotherexample of the magnetic recording medium contemplated by this invention.

FIG. 9 is a cross section illustrating the construction of a furtherexample of the magnetic recording medium contemplated by this invention.

FIG. 10 is a cross section illustrating the construction of anotherexample of the magnetic recording medium contemplated by this invention.

FIG. 11 is a cross section illustrating the construction of stillanother example of the magnetic recording medium contemplated by thisinvention.

FIG. 12 is a schematic diagram illustrating one example of the magneticrecording and reproducing apparatus contemplated by this invention, FIG.12( a) depicting the whole construction and FIG. 12( b) depicting themagnetic head.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a cross section illustrating one example of the configurationof the magnetic recording medium contemplated by the present invention.The magnetic recording medium shown herein has a soft magnetic primarycoat 2, an orientation-controlling layer 3, a perpendicularly magneticlayer 4, a protective layer 5 and a lubricating coat 6 formedsequentially in the order mentioned on a nonmagnetic substrate 1. Thesoft magnetic primary coat 2 and the orientation-controlling layer 3constitute a primary coat. The perpendicularly magnetic layer 4 iscomposed of a magnetic layer 4 a and a magnetic layer 4 b.

As the nonmagnetic substrate 1, a metallic substrate formed of ametallic material, such as aluminum or an aluminum alloy, may be used.Nonmetallic substrates formed of nonmetallic materials, such as glass,ceramic, silicon, silicon carbide and carbon, are also available.

The glass substrates include substrates of materials, such as amorphousglass and glass ceramics. As amorphous glass, general-purpose soda-limeglass and aluminosilicate glass may be used. Then, as the glassceramics, lithium-based glass ceramics may be used. As the ceramicsubstrate, sinters having general-purpose aluminum oxide, aluminumnitride and silicon nitride as main components and fiber-reinforcedcomposites of such sinters may be used.

As the nonmagnetic substrate 1, the composites obtained by forming a Niplayer or NiP alloy layer by the technique of plating or sputtering onthe surface of the metallic substrate or nonmetallic substrate mentionedabove may be used.

The nonmagnetic substrate 1 having an average surface roughness, Ra, of2 nm (20 Å) or less and preferably 1 nm or less proves favorable becausethis surface roughness fits the recording of high recording densityhaving the head floated to a low degree.

The surface having a micro-swell (Wa) of 0.3 nm or less preferably 0.25nm or less) proves favorable because it fits the recording of highrecording density having the head floated to a low degree. The use of anaverage surface roughness, Ra, of 10 nm or less (preferably 9.5 nm orless) for at least either of the chamfered part and the lateral facepart of the end face proves favorable for the sake of the flightstability of the magnetic head. The micro-swell (Wa) can be determined,for example, as the average surface roughness in the range ofmeasurement of 80 μm by using a surface roughness-testing device (madeby KLM-Tencor Corp., U.S.A. and sold under the product code of “P-12”).

The soft magnetic primary coat 2 is provided for the purpose ofenlarging the perpendicular component of the magnetic flux generatedfrom the magnetic head relative to the substrate and fixing thedirection of magnetization of the perpendicularly magnetic layer 4 forrecording information more steadily to the direction perpendicular tothe nonmagnetic substrate 1. This function is at an advantage inbecoming more conspicuous particularly when a single magnetic pole headfor perpendicular recording is used as the magnetic recording andreproducing head.

The soft magnetic primary coat 2 is formed of a soft magnetic material.As the material, materials containing Fe, Ni and Co are available.

As concrete examples of the material, FeCo-based alloys (such as FeCoand FeCoV), FeNi-based alloys (such as FeNi, FeNiMo, FeNiCr and FeNiSi),FeAl-based alloys (such as FeAl, FeAlSi, FeAlSiCr, FeAlSiTiRu andFeAlO), FeCr-based alloys (such as FeCr, FeCrTi and FeCrCu), FeTa-basedalloys (such as FeTa, FeTaC and FeTaN), FeMg-based alloys (such asFeMgO), FeZr-based alloys (such as FeZrN), FeC-based alloys, FeN-basedalloys, FeSi-based alloys, FeP-based alloys, FeNb-based alloys,FeHf-based alloys and FeB-based alloys may be cited.

Materials of microcrystalline structures of FeAlO, FeMgO, FeTaN andFeZrN containing 60 at % or more of Fe, or granular structures havingfine crystal grains dispersed in a matrix, may be used.

As the material for the soft magnetic primary coat 2, Co alloys havingan amorphous structure containing 80 at % or more of Co and containingat least one member selected from the group consisting of Zr, Nb, Ta, Crand Mo may be used besides the materials enumerated above. As preferredconcrete examples of the material of Co alloy, CoZr-, CoZrNb-, CoZrTa-,CoZrCr- and CoZrMo-based alloys may be cited.

The coercive force, Hc, of the soft magnetic primary coat 2 is preferredto be 200 (Oe) or less (preferably 50 (Oe) or less).

If this coercive force, Hc, exceeds the limit mentioned above, theexcess will be at a disadvantage in unduly lowering the soft magneticproperty and suffering the waveform of reproduction to assume a shapedistorted from the so-called rectangular wave.

The saturated magnetic flux density, Bs, of the soft magnetic primarycoat 2 is preferred to be 0.6 T or more (preferably 1 T or more). Ifthis magnitude, Bs, falls short of the limit mentioned above, theshortage is at a disadvantage in compelling the waveform of reproductionto assume a shape distorted from the so-called rectangular wave.

Further, the product Bs·t (T·nm) of the saturated magnetic flux density,Bs (T), of the soft magnetic primary coat 2 multiplied by the thickness,t (nm), of the soft magnetic primary coat 2 is preferred to be 20 (T·nm)or more (preferably 40 (T·nm) or more). If this magnitude, Bs·t, fallsshort of the limit mentioned above, the shortage will be at adisadvantage in causing the waveform of reproduction to deform anddegrading the OW (Over Write) property (writing property).

It is preferred that the outermost surface of the soft magnetic primarycoat 2 (the surface on the orientation-controlling layer 3 side) beformed by having the material forming the soft magnetic primary coat 2partially or wholly oxidized. Preferably, the material forming the softmagnetic primary coat 2 is partially or wholly oxidized or the oxide ofthe material is formed and disposed on the surface of the soft magneticprimary coat 2 (the surface on the orientation-controlling layer 3 side)and in the vicinity thereof, for example.

Since the magnetic fluctuation of the surface of the soft magneticprimary coat 2 is consequently repressed, it is made possible to allaythe noise due to the magnetic fluctuation and improve the read/writeproperty of the magnetic recording medium.

The improvement of the read/write property can otherwise be attained byfinely dividing the crystal grains of the orientation-controlling layer3 formed on the soft magnetic primary coat 2.

The oxidized part of the surface of the soft magnetic primary coat 2 canbe formed by a method which comprises forming a soft magnetic primarycoat 2 and subsequently exposing this primary coat to anoxygen-containing atmosphere or a method which consists in introducingoxygen to the soft magnetic primary coat 2 during the process of moldinginto a film the part of the primary coat approximating the surfacethereof. To be specific, the exposure of the surface of the softmagnetic primary coat 2 to oxygen is accomplished by allowing thesurface to remain in a gaseous atmosphere formed solely of oxygen oroxygen diluted with a gas, such as argon or nitrogen, for a period inthe approximate range of 0.3 to 20 seconds. Otherwise, the surface maybe exposed to the air. Particularly when the gas formed by dilutingoxygen with a gas, such as argon or nitrogen, is used, the production isstably implemented because the degree of oxidization of the surface ofthe soft magnetic primary coat 2 is easily adjusted. When the oxygen isintroduced to the gas being used for molding the soft magnetic substrate1 in the form of a film, the technique of sputtering adopted for themolding of the film may be performed by using a process gasincorporating oxygen therein only in part of the time spent for themolding of film. As the process gas, a gas formed by mixing argon with0.05% to 50% (preferably 0.1 to 20%) of oxygen in volume ratio is usedfavorably.

The orientation-controlling layer 3 is intended to control theorientation and the grain diameter of the perpendicularly magnetic layer4 to be placed directly thereon.

Though the material for this layer does not need to be particularlyrestricted, a material having the hcp structure, fcc structure oramorphous structure proves favorable. Ru-based alloys, Ni-based alloys,Co-based alloys and Pt-based alloys prove particularly favorable.

As the Ni-based alloy, for example, the material formed of at least onekind selected from the group consisting of NiTa alloys, NiNb alloys,NiTi alloys and NiZr alloys containing 33 to 80 at % of Ni provesfavorable. The nonmagnetic material containing 33 to 80 at % of Ni andcontaining one or more elements selected from the group consisting ofSc, Y, Ti, Zr, Hf, Nb, Ta and Co is available likewise. In this case,the Ni content is preferred to fall in the range of 33 at % to 80 at %for the sake of enabling the orientation-controlling layer to retain theinherent effect and avoid acquiring a magnetic property.

For this reason, the magnetic recording medium in the present embodimentis preferred to limit the thickness of the orientation-controlling layer3 in the range of 0.5 to 40 nm (preferably 1 to 20 nm). When thethickness of the orientation-controlling layer 3 is in the range of 0.5to 40 nm (preferably 1 to 20 nm), the perpendicular orientation of theperpendicularly magnetic layer 4 can be particularly heightened and thedistance between the magnetic head and the soft magnetic primary coat 2during the course of recording can be decreased. Thus, the read/writeproperty can be exalted without entailing any decrease of the reproducedsignal resolving power.

If this thickness falls short of the limit mentioned above, the shortagewill result in lowering the perpendicular orientation in theperpendicularly magnetic layer 4 and degrading the read/write propertyand the resistance to thermal fluctuation.

If the thickness exceeds the limit mentioned above, the excess will beat a disadvantage in unduly adding to the magnetic particle diameter ofthe perpendicularly magnetic layer 4 and possibly degrading the noiseproperty. The distance between the magnetic head and the soft magneticprimary coat 2 is enlarged during the course of recording. This increaseof the distance is at a disadvantage in degrading the reproduced signalresolving power and the output of reproduction.

The surface contour of the orientation-controlling layer 3 affects thesurface contours of the perpendicularly magnetic layer 4 and theprotective layer 5. For the purpose of diminishing the surfaceirregularities of the magnetic recording medium and decreasing theflying height of the magnetic head during the course of recording andreproducing operation, the average surface roughness, Ra, of theorientation-controlling layer 3 is preferred to be 2 nm or less.

By controlling the average surface roughness, Ra, to a level of 2 nm orless, it is made possible to diminish the surface irregularities of themagnetic recording medium, attain satisfactory decrease of the flyingheight of the magnetic head during the course of recording andreproducing operation and exalt the recording density.

The gas used for molding the orientation-controlling layer 3 in the formof a film may incorporate therein oxygen and nitrogen. When thesputtering technique is adopted as the method of molding the film, forexample, the gas obtained by mixing argon with about 0.05 to 50%(preferably 0.1-20%) of oxygen in volume ratio and the gas obtained bymixing argon with about 0.01 to 20% (preferably 0.02 to 10%) of nitrogenin volume ratio are favorably used as the process gas.

The orientation-controlling layer may be formed in a structure havingmetal grains dispersed in an oxide, metal nitride or metal carbide. Theformation of this structure is realized by using an alloy materialcontaining an oxide, metal nitride or metal carbide. SiO₂, Al₂O₃, Ta₂O₅,Cr₂O₃, MgO, Y₂O₃ and TiO₂ are available as oxides. AlN, Si₃N₄, TaN andCrN are available as metal nitrides. TaC, BC and SiC are available asmetal carbides. As concrete examples of the alloy, NiTa—SiO₂,RuCo—Ta₂O₅, Ru—SiO₂, Pt—Si₃N₄ and Pd—TaC may be cited.

The content of the oxide, metal nitride or metal carbide in theorientation-controlling layer 3 is preferred to be 4 mol % or more and12 mol % or less based on the amount of the alloy. If the content of theoxide, metal nitride or metal carbide in the orientation-controllinglayer 3 exceeds the upper limit mentioned above, the excess will be at adisadvantage in suffering the formed metal grains to entrain a residueof the oxide, metal nitride or metal carbide, impairing thecrystallinity and the orientation of the metal grains and impairing thecrystallinity and the orientation of the magnetic layer formed on theorientation-controlling layer 3 as well. If the content of the oxide,metal nitride or metal carbide in the orientation-controlling layer 3falls short of the lower limit mentioned above, the shortage is at adisadvantage in preventing the addition of the oxide, metal nitride ormetal carbide from manifesting the effect aimed at.

FIG. 2 is a cross section illustrating the construction of aperpendicularly magnetic layer. The perpendicularly magnetic layer 4 hasthe easily magnetizing axis thereof oriented in the directionperpendicular to the nonmagnetic substrate. It is composed of a magneticlayer 4 a having Co as a main component thereof, containing at least Ptas well and containing an oxide 41 and a magnetic layer 4 b having Co asa main component thereof containing at least Cr as well and containingno oxide.

The magnetic layer 4 a is formed of a material having Co as a maincomponent, containing at least Pt as well and further containing theoxide 41. This oxide 41 is preferred to be an oxide of Cr, Si, Ta, Al,Ti or Mg. Among other oxides enumerated above, Cr₂O₃ and SiO₂ proveparticularly favorable. Further, the magnetic layer 4 a in the presentembodiment contains Pt.

The magnetic layer 4 a is preferred to have magnetic grains (crystalgrains endowed with crystallinity) 42 dispersed therein. The magneticgrains 42 are preferably formed in a columnar structure that verticallypierces the magnetic layer 4 a as illustrated in FIG. 2. By forming thisstructure, it is made possible to enhance the orientation and thecrystallinity of the magnetic grains 42 of the magnetic layer 4 a andconsequently acquire a signal/noise (S/N) ratio suitable forhigh-density recording.

For the acquisition of this structure, the amount of the oxide 41 to becontained constitutes an important factor.

The content of the oxide 41 is preferred to be 3 mol % or more and 12mol % or less based on the total amount of Co, Cr and Pt. Morepreferably, the content is 5 mol % or more and 10 mol % or less.

The range specified above for the content of the oxide in the magneticlayer 4 a is preferable because the oxide can be educed around themagnetic grains 42 during the formation of a layer and used forisolating and finely dividing the magnetic grains 42 (FIG. 2). If thecontent of the oxide exceeds the upper limit of the range mentionedabove, the excess will be at a disadvantage in suffering the oxide tosurvive as a residue in the magnetic grains, impairing the orientationand the crystallinity of the magnetic grains, further inducingdeposition of the oxide 41 above and below the magnetic grains 42 asillustrated in FIG. 3, and consequently preventing the magnetic grains42 from forming a columnar structure vertically piercing the magneticlayer 4 a. If the content of the oxide falls short of the lower limit ofthe range mentioned above, the shortage will be at a disadvantage inpreventing the magnetic grains from being satisfactorily separated andfinely divided and consequently exalting the noise during the course ofrecording and reproducing operation and obstructing the acquisition of asignal/noise (S/N) ratio suitable for high-density recording.

The content of Cr in the magnetic layer 4 a is preferred to be 6 at % ormore and 16 at % or less (more preferably 10 at % or more and 14 at % orless). The reason for specifying the range mentioned above for the Crcontent is that the Cr content in this range is proper for the purposeof preventing the magnetic anisotropy constant, Ku, of the magneticgrains from being unduly lowered, maintaining the magnetization at ahigh level, and consequently enabling the magnetic layer to acquire aread/write property and a property of thermal fluctuation appropriatefor high-density recording.

If the Cr content exceeds the upper limit of the range mentioned above,the excess will be at a disadvantage in unduly lowering the magneticanisotropy constant, Ku, of the magnetic grains and degrading theproperty of thermal fluctuation and degrading the crystallinity and theorientation of the magnetic grains and consequently impairing theread/write property. If the Cr content falls short of the lower limit ofthe range mentioned above, the shortage will be at a disadvantage inunduly heightening the magnetic anisotropy constant, Ku, of the magneticgrains, suffering the perpendicular coercive force to increaseexcessively and compelling the produced magnetic layer to acquire arecording property (OW) incapable of allowing sufficiently writing onthe head during the recording of data and consequently unfit forhigh-density recording.

The Pt content of the magnetic layer 4 a is preferred to be 10 at % ormore and 20 at % or less. The reason for specifying the range mentionedabove for the Pt content is that the magnetic anisotropy constant, Ku,necessary for perpendicularly magnetic layer is obtained, that themagnetic grains manifest fine crystallinity and orientation and that theproperty of thermal fluctuation and the read/write property consequentlyacquired are suitable for high-density recording.

If the Pt content exceeds the upper limit of the range mentioned above,the excess will be at a disadvantage in suffering the magnetic grains toform a layer of fcc structure and possibly impairing the crystallinityand the orientation of the magnetic grains. If the Pt content fallsshort of the lower limit of the range mentioned above, the shortage willbe at a disadvantage in disabling the acquisition of the magneticanisotropy constant, Ku, necessary for obtaining the property of thermalfluctuation proper for high-density recording.

The magnetic layer 4 a is allowed to contain at least one elementselected from the group consisting of B, Ta, Mo, Cu, Nd, W, Nb, Sm, Th,Ru and Re besides Co, Cr, Pt and the oxide. By containing the elementsmentioned above, it is made possible to promote the fine division of themagnetic grains, exalt the crystallinity and the orientation thereof andacquire a read/write property and a property of thermal fluctuationsuitable for high-density recording.

The total content of the elements mentioned above is preferred to be 8at % or less. If this total content exceeds 8 a %, the excess will be ata disadvantage in suffering the magnetic grains to form a phase otherthan the hcp phase therein, causing turbulence of the crystallinity andthe orientation of the magnetic grains, and consequently obstructing theacquisition of a read/write property and a property of thermalfluctuation suitable for high-density recording.

As concrete examples of the material suitable for the magnetic layer 4a, (Co14Cr18Pt)90-SiO₂)10 {90 mol % of a metal composition comprising 14at % of Cr content, 18 at % of Pt content and the balance of Co and 10mol % of an oxide composition comprising SiO₂}, (Co10Cr16Pt)92-(SiO₂)8{92 mol % of a metal composition comprising 10 at % of Cr content, 16 at% of Pt content and the balance of Co and 8 mol % of an oxidecomposition comprising SiO₂}, (Co8Cr14Pt4Nb)94-(Cr₂O₃)_(6 {94) mol % ofa metal composition comprising 8 at % of Cr content, 14 at % of Ptcontent, 4 at % of Nb content and the balance of Co and 6 mol % of anoxide composition comprising Cr₂O₃}, and (CoCrPt)—(Ta₂O₅),(CoCrPtMo)—(TiO), (CoCrPtW)—(TiO₂), (CoCrPtB)—(Al₂O₃),(CoCrPtTaNd)—(MgO), (CoCrPtBCu)—(Y₂O₃) and (CoCrPtRe)—(SiO₂) may becited.

The magnetic layer 4 b is formed of a material having Co as a maincomponent and containing at least Cr. It is preferably formed in astructure having magnetic grains 43 epitaxially grown from the magneticgrains 42 in the magnetic layer 4 a as illustrated in FIG. 2. In thiscase, the magnetic grains 42 of the magnetic layer 4 b and the magneticgrains 43 of the magnetic layer 4 a may form any of the ratios of one toone, plurality to one, and one to plurality.

The epitaxial growth of the magnetic grains 43 of the magnetic layer 4 bfrom the magnetic grains 42 of the magnetic layer 4 a is at an advantagein promoting fine division of the magnetic grains 43 of the magneticlayer 4 b and further exalting the crystallinity and the orientationthereof.

The Cr content of the magnetic layer 4 b is preferred to be 14 at % ormore and 26 at % or less. The specification of the range mentioned abovefor the Cr content is at an advantage in enabling the reproduction ofdata to yield a sufficient output and ensuring acquisition of a properproperty of thermal fluctuation.

If the Cr content exceeds the upper limit of the range mentioned above,the excess will be at a disadvantage in unduly diminishing themagnetization of the magnetic layer 4 b. If this Cr content falls shortof the lower limit of the range mentioned above, the shortage will be ata disadvantage in preventing the magnetic grains from beingsatisfactorily separated and finely divided, suffering the noise duringthe course of recording and reproducing operation to increase andobstructing the acquisition of a signal/noise (S/N) ratio suitable forhigh-density recording.

It is allowed that the magnetic layer 4 b is formed of a materialcontaining Pt besides Co and Cr. The Pt content of the magnetic layer 4b is preferred to be 8 at % or more and 20 at % or less. The reason forspecifying the range mentioned above for the Pt content is that thesatisfactory coercive force suitable for high-density recording isobtained, that the high output of reproduction is maintained during thecourse of recording and reproducing operation and consequently that theread/write property and the property of thermal fluctuation suitable forhigh-density recording are obtained.

If the Pt content exceeds the upper limit of the range mentioned above,the excess will be at a disadvantage in suffering the magnetic layer toform a phase of an fcc structure therein and consequently impairing thecrystallinity and the orientation of the magnetic layer. If the Ptcontent falls short of the lower limit of the range mentioned above, theshortage will be at a disadvantage in obstructing the acquisition of themagnetic anisotropy content, Ku, for obtaining the property of thermalfluctuation suitable for high-density recording.

The magnetic layer 4 b is allowed to contain at least one elementselected from the group consisting of B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb,Ru and Re in addition to Co, Cr, Pt and oxide. By containing the elementmentioned above, the magnetic layer is enabled to promote fine divisionof magnetic grains or enhance the crystallinity and the orientation andacquire a read/write property and a property of thermal fluctuationsuitable for high-density recording.

The total content of the elements mentioned above is preferred to be 8at % or less. If the total content exceeds 8 at %, the excess will be ata disadvantage in suffering the magnetic grains to form a phase otherthan the hcp phase and inducing turbulence of the crystallinity and theorientation of the magnetic grains and consequently impeding theacquisition of a read/write property and a property of thermalfluctuation suitable for high-density recording.

As concrete examples of the material suitable for the magnetic layer 4b, Co16-28Cr {16 to 28 at % of Cr and the balance of Co} in the CoCrsystem, Co14-30Cr1-4Ta {14 to 30 at % of Cr content, 1 to 4 at % of Tacontent and the balance of Co} in the CoCrTa system, Co14-26Cr1-5Ta1-4B{14 to 26 at % of Cr content, 1 to 5 at % of Ta content, 1 to 4 at % ofB content and the balance of Co} in the CoCrTaB system,Co14-30Cr1-5B1-4Nd {14 to 30 at % of Cr content, 1 to 5 at % of Bcontent, 1 to 4 at % of Nd content and the balance of Co} in the CoCrBNdsystem, Co16-24Cr10-18Pt1-6B {16 to 24 at % of Cr content, 10 to 18 at %of Pt content, 1 to 6 at % of B content and the balance of Co} in theCoCrPtB system, Co16-24Cr10-20Pt1-7Cu {16 to 24 at % of Cr content, 10to 20 at % of Pt content, 1 to 7 at % of Cu content and the balance ofCo} in the CoCrPtCu system, Co16-26Cr10-20Pt1-4Ta1-4Nd {16 to 26 at % ofCr content, 10 to 20 at % of Pt content, 1 to 4 at % of Ta content, 1 to4 at % of Nd content and the balance of Co} in the CoCrPrPtTaNd system,Co16-26Cr8-18Pt1-6Nb {16 to 26 at % of Cr content, 8 to 18 at % of Ptcontent, 1 to 6 at % of Nb content and the balance of Co} in theCoCrPtNb system, and CoCrPtBNd, CoCrPtBW, CoCrPtMo, CoCrPtCuRu andCoCrPtRe may be cited.

The perpendicular coercive force (Hc) of the perpendicularly magneticlayer 4 is preferred to be 2500 [Oe] or more. If the coercive forcefalls short of 2500 [Oe], the shortage will be at a disadvantage indegrading the read/write property and particularly the frequencyproperty, impairing the property of thermal fluctuation and renderingthe produced magnetic layer unfit as a high-density recording medium.

The nucleation (−Hn) of the perpendicularly magnetic layer 4 ispreferred to be 1000 [Oe] or more. If the nucleation (Hn) falls short of1000 [Oe], the shortage will be at a disadvantage in rendering theproduced magnetic layer deficient in the property of thermalfluctuation.

The nucleation (−Hn) is expressed by the distance [Oe] from the M axisto the point c in an MH curve obtained as by VSM, in which the point arepresents the point at which the external magnetic field in the processof being decreased from the state in which the magnetization issaturated reaches 0 and the point c represents the point at which theline formed by extending the tangent line of the MH curve at the point bat which the magnetization of the MH curve is 0 intersects the saturatedmagnetization.

Incidentally, the nucleation (−Hn) assumes a positive value when thepoint c falls in the region in which the external magnetic field isnegative (refer to FIG. 4) and a negative value when the point c fallsin the region in which the external magnetic field is positive (refer toFIG. 5).

In the perpendicularly magnetic layer 4, the average particle diameterof the magnetic grains is preferred to fall in the range of 5 to 15 nm.This average particle diameter can be found through observing theperpendicularly magnetic layer 4 under a TEM (transmission electronmicroscope) and processing the observed image.

The thickness of the perpendicularly magnetic layer 4 is preferred tofall in the range of 5 to 40 nm. If the thickness of the perpendicularlymagnetic layer 4 falls short of the lower limit of the range mentionedabove, the shortage would result in obstructing the acquisition of asatisfactory output of reproduction and degrading the property ofthermal fluctuation. If the thickness of the perpendicularly magneticlayer 4 exceeds the upper limit of the range mentioned above, the excesswill be at a disadvantage in enlarging the magnetic grains in theperpendicularly magnetic layer 4, exalting the noise during the courseof recording and reproducing operation and degrading the read/writeproperty represented by the signal/noise (S/N) ratio and the recordingproperty (OW).

The protective layer 5 is intended to prevent the perpendicularlymagnetic layer 4 from corrosion and, at the same time, preventing thesurface of the recording medium from sustaining injury when the magnetichead contacts the medium. It can use any of the materials heretoforeknown to the art For example, a material containing C, SiO₂ and ZrO₂ maybe used.

The thickness of the protective layer 5 falling in the range of 1 to 10nm proves advantageous in terms of high recording density because thisthickness allows a decrease in the distance between the head and themedium.

The lubricating layer 6 is preferred to have a lubricating agent, suchas perfluoropolyether, fluorinated alcohol or fluorinated carboxylicacid, incorporated therein.

The magnetic recording medium of this invention is provided on anonmagnetic substrate 1 with at least an orientation-controlling layer 3for controlling the orientation of a layer placed directly thereon, aperpendicularly magnetic layer 5 having an easily magnetizing axisoriented mainly perpendicularly relative to the nonmagnetic substrate 1,and a protective layer 5 and characterized by the perpendicularlymagnetic layer 4 comprising two or more magnetic layers, at least one ofthe magnetic layers being a magnetic layer 4 a having Co as a maincomponent and containing Cr as well and containing an oxide and anotherthereof being a magnetic layer 4 b having Co as a main component andcontaining Cr and containing no oxide. Owing to this configuration, itis made possible to obtain a medium which promotes fine division andmagnetic isolation of magnetic grains, markedly enhances thesignal/noise (S/N) ratio during the course of reproduction, exalts theproperty of thermal fluctuation by improving the nucleation (−Hn), andpossesses an excellent recording property (OW).

In another mode of embodying this invention, the perpendicularlymagnetic layer 4 may be formed in a structure obtained by forming amagnetic layer 4 b containing no oxide as illustrated in FIG. 6 andforming an oxide-containing magnetic layer 4 a thereon.

This invention allows the perpendicularly magnetic layer 4 to be formedof three or more magnetic layers. For example, it is permissible to formmagnetic layers 4 b-1 and 4 b-2 containing no oxide on anoxide-containing magnetic layer 4 a as illustrated in FIG. 7. It isalternatively permissible to form a magnetic layer 4 b containing nooxide on oxide-containing magnetic layers 4 a-1 and 4 a-2 as illustratedin FIG. 8. It is otherwise permissible to have oxide-containing magneticlayers 4 a-1 and 4 a-1 interposed between the magnetic layers 4 b-1 and4 b-2 containing no oxide and between the magnetic layers 4 b-2 and 4b-3 containing no oxide as illustrated in FIG. 9. Particularly, sincethe combination of various magnetic materials results in facilitatingthe control and the adjustment of various properties, such as theproperty of thermal fluctuation, recording property (OW) andsignal/noise (S/N) ratio, it is especially advantageous to have theperpendicularly magnetic layer 4 formed with three or more layers.

This invention allows the perpendicularly magnetic layer 4 to havenonmagnetic layers interposed one each between the component magneticlayers thereof. This structure results in preventing the magnetic grainsfrom being enlarged, enabling the particle diameter to be controlled andconsequently exalting the signal/noise (S/N) ratio further. It ispermissible to have a nonmagnetic layer 91 interposed between themagnetic layers 4 b-1 and 4 b-2 containing no oxide and have anonmagnetic layer 92 interposed between the magnetic layers 4 a-1 and 4l-2 each containing an oxide and placed thereon as illustrated in FIG.10.

The nonmagnetic layer 9 to be interposed between the component magneticlayers of the perpendicularly magnetic layer 4 is preferred to use amaterial possessing an hcp structure. It is advantageous to use a CoCralloy or a CoCrX1 alloy (wherein X1 denotes at least one elementselected from the group consisting of Pt, Ta, Zr, Re, Ru, Cu, Nb, Ni,Mn, Ge, Si, O, N, W, Mo, Ti, V, Zr and B), for example.

The Co content of the nonmagnetic layer 9 to be interposed between thecomponent magnetic layers of the perpendicularly magnetic layer 4 ispreferred to fall in the range of 30 to 70 at %. The reason for thisrange is that the nonmagnetic layer 9 having this Co content assumes anonmagnetic property.

As the alloy possessing an hcp structure and used for the nonmagneticlayer 9 to be interposed between the component magnetic layers of theperpendicularly magnetic layer 4, alloys of Ru, Re, Ti, Y, Hf and Zn areavailable.

Then, as the nonmagnetic layer 9 to be interposed between the componentmagnetic layers of the perpendicularly magnetic layer 4, a metal or analloy assuming other structure may be used in an amount falling in therange in which the crystallinity and the orientation of the magneticlayers vertically opposed across the interposed layer are not impaired.As concrete examples of the material for the nonmagnetic layer 9,elements, such as Pd, Pt, Cu, Ag, Au, Ir, Mo, W, Ta, Nb, V, Bi, Sn, Si,Al, C, B and Cr, and alloys thereof may be cited. Particularly, as Cralloys, it is proper to use CrX2 (wherein X2 denotes one or moreelements selected from the group consisting of Ti, W, Mo, Nb, Ta, Si,Al, B, C and Zc) alloys. In this case, the Cr content is preferred to be60 at % or more.

The nonmagnetic layer 9 to be interposed between the component magneticlayers constituting the perpendicularly magnetic layer 4 may be formedin a structure having the metal grains of the alloy mentioned abovedispersed in an oxide, a metal nitride or a metal carbide. Moreadvantageously, the metal grains possess a columnar structure verticallypiercing the nonmagnetic layer 9. The formation of this structure isrealized by using an alloy material containing an oxide. SiO₂, Al₂O₃,Ta₂Os, Cr₂O₃, MgO, Y₂O₃, and TiO₂ are usable as oxides, AlN, Si₃N₄, TaNand CrN as metal nitrides, and TaC, BC and SiC as metal carbides. Asconcrete examples of the alloy, CoCr—SiO₂, CoCrPt—Ta₂O₅, Ru—SiO₂,Ru—Si₃N₄ and Pd—TaC may be cited.

The content of an oxide, a metal nitride or a metal carbide in thenonmagnetic layer 9 to be interposed between the component magneticlayers of the perpendicularly magnetic layer 4 is preferred to be 4 mol% or more and 12 mol % or less based on the amount of the alloy. If thecontent of the oxide, metal nitride or metal carbide in the nonmagneticlayer 9 exceeds the upper limit of the range mentioned above, the excesswill be at a disadvantage in suffering the metal grains to retain theoxide, metal nitride or metal carbide as a residue, impairing thecrystallinity and the orientation of the metal grains, inevitablyinducing precipitation of the oxide, metal nitride or metal carbideabove and below the metal grains, allowing the metal grains to form acolumnar structure vertically piercing the nonmagnetic layer 9 only withdifficulty and possibly impairing the crystallinity and the orientationof the magnetic layer formed on the nonmetallic layer 9. If the contentof the oxide, metal nitride or metal carbide in the nonmagnetic layer 9falls short of the lower limit of the range mentioned above, theshortage is at a disadvantage in preventing the addition of the oxide,metal nitride or metal carbide from manifesting the effect thereof.

The thickness of the nonmagnetic layer 9 is preferred to be 10 nm orless (more preferably 5 nm or less) lest the enlarged magnetic grains inthe perpendicularly magnetic layer 4 should degrade the signal/noise(S/N) ratio during the course of reproduction or the increased distancebetween the magnetic head and the soft magnetic primary coat 2 shouldinduce degradation of the recording property (OW) and the resolvingpower.

In another mode of embodying this invention, an intermediate layer 8 maybe interposed between the orientation-controlling layer 3 and theperpendicularly magnetic layer 4 as illustrated in FIG. 11 with theobject of enhancing the crystallinity and the orientation of theperpendicularly magnetic layer 4.

The intermediate layer 8 is preferably formed of a material thatpossesses an hcp structure. It is advantageous to use a CoCr alloy or aCrX1 alloy (wherein X1 denotes one or more elements selected from thegroup consisting of Pt, Ta, Zr, Re, Ru, Cu, Nb, Ni, Mn, Ge, Si, O, N, W,Mo, Ti, V, Zr and B) for the intermediate layer 8.

The Co content of the intermediate layer 8 is preferred to fall in therange of 30 to 70 at %. The reason for specifying this range is that theintermediate layer 8 retains a nonmagnetic property when the Co contentis in this range.

The intermediate layer 8 may be formed in a structure having the metalgrains of the alloy mentioned above dispersed in the oxide, metalnitride or metal carbide. More advantageously the metal grains possess acolumnar structure vertically piercing the intermediate layer 8. Byassuming this structure, the intermediate layer 8 is enabled to use analloy material containing an oxide. SiO₂, Al₂O₃, Ta₂Os, Cr₂O₃, MgO, Y₂O₃and TiO₂ are usable as oxides, AlN, Si₃N₄, TaN and CrN as metalnitrides, and TaC, BC and SiC as metal carbides. As concrete examples ofthe alloy, CoCr—SiO₂, CoCrPt—Ta₂O₅, CoCrRu—SiO₂, CoCrRu—Si₃N₄ andCoCrPt—TaC may be cited.

The content of the oxide, metal nitride or metal carbide in theintermediate layer 8 is preferred to be 4 mol % or more and 12 mol % orless based on the amount of the alloy. If the content of the oxide,metal nitride or metal carbide in the intermediate layer 8 exceeds theupper limit of the range mentioned above, the excess will be at adisadvantage in suffering the metal grains to retain the oxide, metalnitride or metal carbide as a residue, impairing the crystallinity andthe orientation of the metal grains, inevitably inducing precipitationof the oxide, metal nitride or metal carbide above and below the metalgrains, allowing the metal grains to form a columnar structurevertically piercing the intermediate layer 8 only with difficulty andpossibly impairing the crystallinity and the orientation of the magneticlayer formed on the intermediate layer 8. If the content of the oxide,metal nitride or metal carbide in the intermediate layer 8 falls shortof the lower limit of the range mentioned above, the shortage will be ata disadvantage in preventing the addition of the oxide, metal nitride ormetal carbide from manifesting the effect thereof.

The thickness of the intermediate layer 8 is preferred to be 20 nm orless (more preferably 10 nm or less) lest the enlarged magnetic grainsin the perpendicularly magnetic layer 4 should degrade the signal/noise(S/N) ratio during the course of reproduction or the increased distancebetween the magnetic head and the soft magnetic primary coat 2 shouldinduce degradation of the recording property (OW) and the resolvingpower.

Now, one example of the method for producing a magnetic recording mediumof the aforementioned construction (the mode of FIG. 1) will bedescribed below.

To produce the magnetic recording medium of the construction mentionedabove, a soft magnetic primary coat 2, an orientation-controlling layer3 and a perpendicularly magnetic layer 4 are sequentially formedrespectively by the sputtering technique, vacuum evaporation techniqueor ion-plating technique on a nonmagnetic substrate 1. Subsequently, aprotective layer 5 is formed preferably by the plasma CVD technique, ionbeam technique or sputtering technique.

The formation of the perpendicularly magnetic layer 4 may be implementedby forming an oxide-containing magnetic layer 4 a, then subjecting theformed layer to a heat treatment and subsequently forming a magneticlayer 4 b containing no oxide. The perpendicularly magnetic layer 4consequently formed may be subjected to an annealing treatment with theobject of enhancing the crystallinity of the magnetic grains.

As the nonmagnetic substrate 1, a metal substrate is formed of ametallic material, such as aluminum or an aluminum alloy. A nonmetallicsubstrate formed of a nonmetallic material, such as glass, ceramic,silicon, silicon carbide or carbon, may be used instead.

The glass substrate is known in various kinds including amorphous glassand glass ceramics, for example. As the amorphous glass, general-purposesoda lime glass and aluminosilicate glass are usable. As the glassceramics, lithium-based glass ceramics are usable. As the ceramicsubstrate, sinters have general-purpose aluminum oxide, aluminum nitrideand silicon nitride as main components and fiber-reinforced products ofsuch sinters are usable.

As the nonmagnetic substrate 1, the products obtained by forming a NiPlayer on the surfaces of the metallic substrate and nonmetallicsubstrate mentioned above by the plating technique or the sputteringtechnique are usable.

The nonmagnetic substrate has an average surface roughness, Ra, of 2 nm(20 Å) or less. This is a favorable restriction in fitting thehigh-density recording with only a low floatation of the head.

Further, the micro-swell (Wa) of the surface is 0.3 nm or less(preferably 0.25 nm or less). This is a favorable restriction in fittingthe high-density recording with only a low floatation of the head. Atleast one of the chamfered part and the lateral surface part of the endface has an average surface roughness, Ra, of 10 nm or less (preferably9.5 nm or less). The adherence to this restriction is favorable for thesake of flight stability of the magnetic head. The micro-swell (Wa) canbe determined, for example, as an average surface roughness accuratelywithin 80 μm by using a surface roughness-testing device (made byKLM-Tencor Corp., U.S.A. and sold under the product code of “P-12”).

The nonmagnetic substrate 1, when necessary, is washed and the washednonmagnetic substrate 1 is disposed inside the chamber of a film-formingdevice.

On the nonmagnetic substrate 1, the soft magnetic primary coat 2, theorientation-controlling layer and the perpendicularly magnetic layer 4are formed by the DC or RF magnetron sputtering technique usingsputtering targets formed of materials identical in composition with thematerials of the relevant layers. The following conditions are adoptedfor the sputtering required for forming the relevant films. The chamberto be used for the film formation is evacuated till the degree of vacuumreaches a level in the range of 10⁻⁴ to 10⁻⁷ Pa. The chamber admits thenonmagnetic substrate and then introduces an Ar gas, for example, as asputtering gas and effects electric discharge to induce formation of afilm by sputtering. The power supplied in this case is set at a level inthe range of 0.1 to 2 kW. By adjusting the duration of the electricdischarge and the magnitude of the power supplied, it is made possibleto obtain the film in an expected thickness.

It is preferred that the soft magnetic primary coat 2 is formed in athickness in the range of 50 to 400 nm by adjusting the duration of theelectric discharge and the magnitude of the power.

In the formation of the soft magnetic primary coat 2, the use of asputtering target made of a soft magnetic material is favorable infacilitating the formation of the soft magnetic primary coat. Asconcrete examples of the soft magnetic material, FeCo-based alloys (suchas FeCo and FeCoV), FeNi-based alloys (such as FeNi, FeNiMo, FeNiCr andFeNiSi), FeAl-based alloys (such as FeAl, FeAlSi, FeAlSiCr, FeAlSiTiRuand FeAlO), FeCr-based alloys (such as FeCr, FeCrTi and FeCrCu),FeTa-based alloys (such as FeTa, FeTaC and FeTaN), FeMg-based alloys(such as FeMgO), FeZr-based alloys (such as FeZrN), FeC-based alloys,FeN-based alloys, FeSi-based alloys, FeP-based alloys, FeNb-basedalloys, FeHf-based alloys, FeB-based alloys, and FeAlO, FeMgO, FeTaN andFeZrN which contain 60 at % or more of Fe may be cited. Further, CoZr-,CoZrNb-, CoZrTa-, CoZrCr- and CoZrMo-based alloys which contain 80 at %or more of Co, contains at least one element selected from among Zr, Nb,Ta, Cr and Mo and possessing an amorphous structure may be cited asconcrete examples of particularly preferred alloys.

The target mentioned above is an alloy target or a sintered alloy targetproduced by the fusing technique.

After the soft magnetic primary coat 2 has been formed, theorientation-controlling layer is formed in a thickness in the range of0.5 to 40 nm (preferably 1 to 20 nm) by adjusting the duration of theelectric discharge and the magnitude of the power supplied. As concreteexamples of the material for the sputtering target to be used in theformation of the orientation-controlling layer 3, Ru-based alloys,Ni-based alloys and Co-based alloys may be cited.

Next, the perpendicularly magnetic layer 4 is formed.

First, the oxide-containing magnetic layer 4 a is formed similarly bythe sputtering technique using a sputtering target As concrete examplesof the sputtering target to be used herein, (Co14Cr18Pt)90-(SiO₂)10 {90mol % of a metal composition comprising 14 at % of Cr content, 18 at %of Pt content and the balance of Co and 10 mol % of an oxide compositionconsisting of SiO₂}, (Co10Cr16Pt)92-(SiO₂)8 {92 mol % of a metalcomposition comprising 10 at % of Cr content, 16 at % of Pt content andthe balance of Co and 8 mol % of an oxide composition consisting ofSiO₂}, (Co8Cr14Pt4Nb)94-Cr₂O₃)6 {94 mol % of a metal compositioncomprising 8 at % of Cr content, 14 at % of Pt content, 4 at % of Nbcontent and the balance of Co and 6 mol % of an oxide compositionconsisting of Cr₂O₃} and (CoCrPt)—(Ta₃O₅), (CoCrPtMo)—(TiO),(CoCrPtW)—(TiO₂), (CoCrPtB)—(Al₂O₃), (CoCrPtTaNd)—(MgO),(CoCrPtBCu)—(Y₂O₃) and (CoCrPtRe)—(SiO₂) may be cited.

The content of the oxide is preferred to be 3 mol % or more and 12 mol %or less based on the total amount of Co, Cr and Pt. More preferably,this content is 5 mol % or more and 10 mol % or less.

The reason for specifying the aforementioned range for the content ofthe oxide in the magnetic layer 4 a is that the particular contentpermits the oxide to be precipitated around the magnetic grains and theisolation and fine division of the magnetic grains to be attained duringthe formation of the relevant layer. If the content of the oxide exceedsthe upper limit of the range mentioned above, the excess will be at adisadvantage in suffering the oxide to survive as a residue in themagnetic grains, impairing the orientation and the crystallinity of themagnetic grains, inducing the precipitation of an oxide 41 above andbelow magnetic grains 42 as illustrated in FIG. 3 and consequentlypreventing the magnetic grains 42 from forming a columnar structurevertically piercing the magnetic layer 4 a (the structure of FIG. 2). Ifthe content of the oxide falls short of the lower limit of the rangementioned above, the shortage will be at a disadvantage in preventingthe magnetic grains from satisfactory separation and fine division,consequently exalting the noise during the course of recording andreproducing operation and disabling the acquisition of the signal/noise(S/N) ratio suitable for high-density recording.

The magnetic layer 4 a is preferred to have magnetic grains 42 dispersedin the layer as illustrated in FIG. 2. Further, the magnetic grains 42are preferred to form a columnar structure (the structure of FIG. 2)vertically piercing the magnetic layer 4 a. The formation of thisstructure necessitates the following conditions besides the use of sucha target material as described above.

The sputtering film formation is carried out by using a target made of amaterial having Co as a main component, containing at least Cr as welland containing an oxide, preparing the chamber for the film formation ina state evacuated till the degree of vacuum reaches a level in the rangeof 10⁻⁴ to 10⁻⁷ Pa and introducing an Ar gas as the sputtering gas intothe chamber and operating the chamber so as to form a film bysputtering. The power to be supplied in this case is set at a level inthe range of 0.1 kW to 1 kW. The film of an expected thickness isobtained by adjusting the duration of the electric discharge and themagnitude of the power to be supplied.

In this case, the pressure of the sputtering gas is preferred to be 3 Paor more and 20 Pa or less. Preferably, the power of electric dischargeis set at the lowest possible level and the duration of film formationis elongated to the fullest extent allowed in terms of process. Thereason for adopting these conditions is that they enable the magneticgrains to be dispersed in the oxide and allow the magnetic grains toform easily the columnar structure vertically piercing the magneticlayer 4 a.

Argon is used as the sputtering gas in the formation of theoxide-containing magnetic layer 4 a. Optionally, this sputtering gas mayincorporate therein nitrogen gas or oxygen gas, or both.

The addition of nitrogen or oxygen, or both, may be accomplished byusing a mixed gas that comprises argon and the additive gases or byseparately introducing the component gases of the mixed gas into thechamber and mixing them in the chamber.

The amount of nitrogen or oxygen, or both, to be added is preferred tobe 20 vol % or less (preferably 10 vol % or less) based on the volume ofargon. If the amount of nitrogen or oxygen to be added exceeds the limitmentioned above, the excess will be at a disadvantage in impairing thecrystallinity and the orientation of the magnetic grains and, as aresult, possibly degrading the read/write property.

As regards the conditions to be adopted when the material of(Co14Cr18Pt)90-(SiO₂)10 {90 mol % of a metal composition comprising 14at % of Cr content, 18 at % of Pt content and the balance of Co and 10mol % of an oxide composition consisting of SiO₂} is used for themagnetic layer 4 a, the power of sputtering electric discharge ispreferred to be 0.4 kW, the pressure to be in the range of 6 to 8 Pa,and the amount of oxygen to be added to be in the range of 1 to 2 vol %.

During the formation of the magnetic layer 4 a, a negative voltage(substrate bias) may be applied to the nonmagnetic substrate 1. By thisapplication of the negative voltage, it is made possible to promoteseparation of the magnetic grains and the oxide, induce fine divisionand isolation of the magnetic grains to a greater extent and permit theacquisition of a read/write property more suitable for high-densityrecording.

It is preferred that the substrate bias is applied in the range of −100V to −600 V. If the bias exceeds the upper limit of the range mentionedabove, the excess will be at a disadvantage in possibly impairing thecrystallinity and the orientation of the magnetic grains. If the biasfalls short of the lower limit of the range mentioned above, theshortage is at a disadvantage in preventing the use of the bias frommanifesting the effect aimed at

Next, the magnetic layer 4 b containing no oxide is formed similarly bythe sputtering technique using a sputtering target As concrete examplesof the material suitable for the magnetic layer 4 b, Co16-28Cr {16 to 28at % of Cr content and the balance of Co} as the CoCr system,Co14-30Cr1-4Ta {14 to 30 at % of Cr content, 1 to 4 at % of Ta contentand the balance of Co} as the CoCrTa system, Co14-26Cr1-5Ta1-4B {14 to26 at % of Cr content, 1 to 5 at % of Ta content, 1 to 4 at % of Bcontent and the balance of Co} as the CoCrTaB system, Co14-30Cr1-5B1-4Nd{14 to 30 at % of Cr content, 1 to 5 at % of B content, 1 to 4 at % ofNd content and the balance of Co} as the CoCrBNd system,Co16-24Cr10-18Pt1-6B {16 to 24 at % of Cr content, 10 to 18 at % of Ptcontent, 1 to 6 at % of B content and the balance of Co} as the CoCrPtBsystem, Co16-24Cr10-20Pt1-7Cu {16 to 24 at % of Cr content, 10 to 20 at% of Pt content, 1 to 7 at % of Cu content and the balance of Co} as theCoCrPtCu system, Co16-26Cr10-20Pt1-4Ta1-4Nd {16 to 26 at % of Crcontent, 10 to 20 at % of Pt content, 1 to 4 at % of Ta content, 1 to 4at % of Nd content and the balance of Co} as the CoCrPtTaNd system,Co16-26Cr8-18Pt1-6Nb {16 to 26 at % of Cr content, 8 to 18 at % of Ptcontent, 1 to 6 at % of Nb content and the balance of Co} as theCoCrPtNb system, and CoCrPtBNd, CoCrPtBW, CoCrPtMo, CoCrPtCuRu andCoCrPtRe may be cited.

The following conditions, for example, are adopted for the formation ofthe magnetic layer 4 b.

The sputtering film formation is carried out by using a target made of amaterial having Co as a main component, containing at least Cr as welland containing no oxide, preparing the chamber for the film formation ina state evacuated till the degree of vacuum reaches a level in the rangeof 10⁻⁴ to 10⁻⁷ Pa, introducing an Ar gas as the sputtering gas into thechamber and operating the chamber so as to form a film by sputtering.The power to be supplied in this case is set at a level in the range of0.1 kW to 2 kW. The film of an expected thickness is obtained byadjusting the duration of the electric discharge and the magnitude ofthe power to be supplied.

In this case, the pressure of the sputtering gas is preferred to be 20Pa or less.

In the formation of the magnetic layer 4 b containing no oxide, argon isused as the sputtering gas. Optionally, this sputtering gas mayincorporate therein nitrogen gas or oxygen gas, or both.

The addition of nitrogen or oxygen, or both, may be accomplished byusing a mixed gas that comprises argon and the additive gas or byseparately introducing the component gases of this mixed gas into thechamber and mixing them in the chamber.

The amount of nitrogen or oxygen or both to be added is preferred to be20 vol % or less (preferably 10 vol % or less) based on the volume ofargon. If the amount of nitrogen or oxygen to be added exceeds the limitmentioned above, the excess will be at a disadvantage in impairing thecrystallinity and the orientation of the magnetic grains and, as aresult, possibly degrading the read/write property.

The formation of the magnetic layer 4 b may be preceded by applicationof heat. This application of heat is carried out in vacuum.

Though the temperature of the heat application does not need to beparticularly restricted, it is preferred to fall in a range in which theheat applied does not change the shape of the nonmagnetic layer 1. Whenamorphous glass is adopted, for example, the temperature is preferred tobe 300° C. or less.

By forming the magnetic layer 4 b in a heated state, it is made possibleto induce segregation of Cr in the magnetic layer 4 b, promote finedivision and isolation of the magnetic grains to a further extent andconsequently enhance the read/write property. Since the adoption of theheated state is so favorable, it may be executed as occasion demands.

As regards the conditions to be adopted when the material ofCo16Cr12Pt4B {16 at % of Cr content, 12 at % of Pt content, 4 at % of Bcontent and the balance of Co} is used for the magnetic layer 4 b, theheating temperature is preferred to fall in the approximate range of180° C. to 220° C., the power of sputtering electric charge to be 1 kWor less and the pressure to be in the range of 2 to 5 Pa, and no gas isadded.

During the formation of the magnetic layer 4 b, a negative voltage(substrate bias) may be applied to the nonmagnetic substrate 1. By thisapplication of the negative voltage, it is made possible to induce finedivision and isolation of the magnetic grains and permit the acquisitionof a read/write property more suitable for high-density recording.

It is preferred that the substrate bias is applied in the range of −100V to −600 V. If the bias exceeds the upper limit of the range mentionedabove, the excess will be at a disadvantage in possibly impairing thecrystallinity and the orientation of the magnetic grains. If the biasfalls short of the lower limit of the range mentioned above, theshortage would be at a disadvantage in preventing the use of the biasfrom manifesting the effect aimed at.

After the perpendicularly magnetic layer 4 has been formed, theprotective layer 5, such as the protective layer 5 having carbon as amain component, is formed through the sputtering technique or the plasmaCVD technique or the combination of these techniques.

Further, the protective layer, when necessary, may be coated with afluorine-based lubricating agent, such as perfluoropolyether, by thedipping technique or the spin coating technique so as to give rise to alubricating layer 6.

The magnetic recording medium produced by this invention is provided ona nonmagnetic substrate 1 with at least an orientation-controlling layer3 for controlling the orientation of a layer formed directly thereon, aperpendicularly magnetic layer 4 having an easily magnetizing axisoriented mainly perpendicularly relative to the nonmagnetic substrate 1,and a protective layer 5 and characterized by the perpendicularlymagnetic layer comprising two or more magnetic layers, at least one ofthe magnetic layers being a layer 4 a having Co as a main component andcontaining Pt as well and containing an oxide and at least another ofthe magnetic layers being a layer 4 b having Co as a main component andcontaining Cr as well and containing no oxide. Owing to thisconfiguration, it is made possible to promote fine division and magneticisolation of the magnetic grains, enhance the signal/noise (S/N) ratiogreatly during the course of reproduction, also exalt the nucleation(−Hn) and consequently heighten the property of thermal fluctuation, andobtain a medium possessing an outstanding recording property (OW).

FIG. 12 is a schematic diagram illustrating one example of the magneticrecording and reproducing apparatus contemplated by this invention; FIG.12( a) depicting the whole construction and FIG. 12( b) the magnetichead. The magnetic recording and reproducing apparatus illustrated hereis furnished with a magnetic recording medium 10 possessing theconstruction shown in FIG. 1, a medium-driving part 11 for rotationallydriving the magnetic recording medium 10, a magnetic head 12 forrecording and reproducing information in the magnetic recording medium10, a head-driving part 13 for moving the magnetic head 12 relative tothe magnetic recording medium 10, and a recording and reproducingsignal-processing system 14. The recording and reproducingsignal-processing system 14 is adapted to process data received from theexterior, send the recording signal to the magnetic head 12, process thereproducing signal from the magnetic head 12, and send the processeddata to the exterior. As the magnetic head 12 to be used in the magneticrecording and reproducing apparatus of this invention, a head that isprovided as the reproducing element with a GMR element utilizing thegiant magnetic resistance (GMR) effect and adapted for higher recordingdensity can be utilized.

According to the magnetic recording and reproducing apparatus mentionedabove, since the magnetic recording medium of this invention is used forthe magnetic recording medium 10, it is made possible to promote finedivision and magnetic isolation of the magnetic grains, enhance greatlythe signal/noise (S/N) ratio during the course of reproduction, enhancethe nucleation (−Hn) and consequently exalt the property of thermalfluctuation, further permit the acquisition of a medium endowed with anoutstanding recording property (OW), and complete an excellent magneticrecording and reproducing apparatus suitable for high-density recording.

EXAMPLE 1

A film-forming chamber of a DC magnetron sputtering device (made byANELVA Corp., JAPAN and sold under the product code of “C-3010”)admitted a washed glass substrate (2.5 inches in outer length, productof Ohara K.K., JAPAN), and was evacuated till the degree of vacuumreached 1×10⁻⁵ Pa and then operated to effect sputtering by using atarget of Co4Zr7Nb {4 at % of Zr content, 7 at % of Nb content and thebalance of Co} at a substrate temperature of 100° C. or less to form asoft magnetic primary coat 2 of a thickness of 100 nm on the glasssubstrate. By a test with a vibration system magnetic property testingdevice (VSM), the product, Bs·t (T·nm) of the saturated magnetic fluxdensity Bs (T) multiplied by the film thickness t (nm) of this film wasconfirmed to be 120 (T·nm).

On the soft magnetic primary coat 2 mentioned above, a Ni40Ta {40 at %of Ta content and the balance of Ni} target and a Ru target weresequentially deposited in a thickness of 5 nm and 20 nm, respectively,to give rise to an orientation-controlling layer 3.

On the orientation-controlling layer, a target formed of(Co14Cr18Pt)90-SiO₂)10 {90 mol % of an alloy composition comprising 14at % of Cr content, 18 at % of Pt content and the balance of Co and 10mol % of an oxide consisting of SiO₂} was deposited by sputtering undera pressure of 0.7 Pa to form a magnetic layer 4 a in a thickness of 10nm.

Next, a target formed of Co16Cr12Pt4B {16 at % of Cr content, 12 at % ofPt content, 4 at % of B content and the balance of Co} was deposited bysputtering under a pressure of 3 Pa to form a magnetic layer 4 b in athickness of 10 nm.

Subsequently, a protective layer 5 was formed in a thickness of 5 nm bythe CVD technique. Then, a lubricating layer 6 formed ofperfluoropolyether was formed by the dipping technique to obtain amagnetic recording medium.

The magnetic recording medium consequently obtained was rated formagnetic properties by the use of a Kerr effect-testing device andtested for coercive force (Hc) and nucleation (−Hn).

The read/write property was determined by the use of a read-writeanalyzer RWA1632 and a spin stand S1701MP made by GUZIK Corp of U.S.A.The head used herein was furnished with a writing single magnetic poleand a GMR element that was intended to function in the reproducing unit.

The signal/noise (S/N) ratio was tested at a recording density of 700kFCI.

The recording property (OW) was determined by first writing a signal of700 kFCI, then superposing a signal of 116 kFCI, extracting a highfrequency component with a frequency filter and rating the data-writingability based on the ratio of residue.

The property of thermal fluctuation was determined by performing awriting at a recording density of 50 kFCI under the condition of 70° C.and then computing the attenuation ratio of the output relative to thereproducing output one second after the writing on the basis of(So−S)×100/(So×3). In this formula, the So denotes the reproductionoutput after the elapse of one second after the writing and S denotesthe reproducing output after the elapse of 1000 seconds. The results areshown in the column of Example 1 in Table 1.

TABLE 1 Magnetic layer 4 Magnetic layer 4a Magnetic layer 4b Film- Film-Composition forming Composition forming {(at %) mol %} Thicknesspressure (at %) Thickness pressure Ex. 1 {(Co14Cr18Pt)90-(SiO₂)10} 10(nm) 0.7 (Pa) (Co16Cr12Pt4B) 10 (nm) 3 (Pa) Ex. 2 Same as above 10 2Same as above 10 3 Ex. 3 Same as above 10 4 Same as above 10 3 Ex. 4Same as above 10 6 Same as above 10 3 Ex. 5 Same as above 10 8 Same asabove 10 3 Ex. 6 Same as above 10 11 Same as above 10 3 Ex. 7 Same asabove 10 8 Same as above 10 0.6 Ex. 8 Same as above 10 8 Same as above10 5 Ex. 9 {(Co14Cr18Pt)98-(SiO₂)2} 10 8 Same as above 10 3 Ex. 10{(Co14Cr18Pt)97-(SiO₂)3} 10 8 Same as above 10 3 Ex. 11{(Co14Cr18Pt)93-(SiO₂)7} 10 8 Same as above 10 3 Ex. 12{(Co14Cr18Pt)88-(SiO₂)12} 10 8 Same as above 10 3 Ex. 13{(Co14Cr18Pt)85-(SiO₂)15} 10 8 Same as above 10 3 Ex. 14{(Co4Cr18Pt)90-(SiO₂)10} 10 8 Same as above 10 3 Ex. 15{(Co6Cr18Pt)90-(SiO₂)10} 10 8 Same as above 10 3 Ex. 16{(Co16Cr18Pt)90-(SiO₂)10} 10 8 Same as above 10 3 Ex. 17{(Co20Cr18Pt)90-(SiO₂)10} 10 8 Same as above 10 3 Ex. 18{(Co14Cr8Pt)90-(SiO₂)10} 10 8 Same as above 10 3 Ex. 19{(Co14Cr10Pt)90-(SiO₂)10} 10 8 Same as above 10 3 Ex. 20{(Co14Cr22Pt)90-(SiO₂)10} 10 8 Same as above 10 3 Comp. Ex. 1{(Co14Cr18Pt)90-(SiO₂)10} 10 8 — — — Comp. Ex. 2 Same as above 20 8 — —— Comp. Ex. 3 (Co14Cr18Pt) 10 0.7 (Co16Cr12Pt4B) 10 3 Comp. Ex. 4 — — —Same as above 10 3 Comp. Ex. 5 — — — Same as above 20 3 Comp. Ex. 6{(Co14Cr18Pt)90-(SiO₂)10} 10 8 (Co14Pt) 10 0.7 Comp. Ex. 7 Same as above10 8 (Co12Cr) 10 0.7 Comp. Ex. 8 Same as above 10 8 (Fe50Pt) 10 0.7Comp. Ex. 9 Same as above 10 8 {Co(0.2 nm)/Pd(0.5 nm)}10  7 3 Comp. Ex.10 Same as above 8 {Co(0.2 nm)/Pd(0.5 nm)}20 14 3 Magnetic propertiesStatic magnetic Read/write Property of thermal property Propertyfluctuation Coercive force −Hn Ow S/N (% decade) Ex. 1 3400(Oe) 1800(Oe)48.5(dB) 19.8(dB) 0.10 Ex. 2 3500 1800 48.0 20.3 0.09 Ex. 3 3700 185046.5 20.8 0.09 Ex. 4 3800 1850 46.0 21.4 0.09 Ex. 5 4100 1900 46.0 22.00.08 Ex. 6 3900 1750 48.5 21.1 0.09 Ex. 7 4000 1750 47.0 21.3 0.09 Ex. 83950 1800 45.5 21.5 0.09 Ex. 9 3300 1000 52.0 16.5 0.24 Ex. 10 3400 135054.5 17.8 0.13 Ex. 11 3850 1550 52.0 19.1 0.11 Ex. 12 3750 1600 53.518.8 0.11 Ex. 13 3600 1200 52.0 17.5 0.16 Ex. 14 4500 2200 42.5 20.80.05 Ex. 15 4300 2100 44.0 20.9 0.06 Ex. 16 3500 1400 53.0 20.7 0.11 Ex.17 3300 1100 54.0 20.1 0.14 Ex. 18 3400 1000 56.0 19.6 0.19 Ex. 19 36001200 54.0 19.9 0.16 Ex. 20 4500 1600 49.0 19.3 0.12 Comp. Ex. 1 4650 80034.5 16.5 0.45 Comp. Ex. 2 5700 900 21.5 12.3 0.40 Comp. Ex. 3 2600 70051.0 12.2 0.47 Comp. Ex. 4 2750 100 57.0 13.4 0.70 Comp. Ex. 5 2800 10057.0 11.2 0.63 Comp. Ex. 6 2500 300 42.5 12.9 0.45 Comp. Ex. 7 2200 043.2 11.3 0.67 Comp. Ex. 8 1800 −200 47.0  5.7 1.12 Comp. Ex. 9 3700 90034.0 14.6 0.38 Comp. Ex. 10 4300 1000 29.0 11.2 0.33

EXAMPLES 2 TO 20

Magnetic recording media were manufactured by following the procedure ofExample 1 while changing the magnetic layer 4 a and the magnetic layer 4b to the compositions and conditions indicated in the columns ofExamples 2 to 20 in Table 1. The results of the rating of these magneticrecording media are shown in Table 1.

COMPARATIVE EXAMPLES 1 TO 7

Magnetic recording media were manufactured by following the procedure ofExample 1 while changing the magnetic layer 4 a and the magnetic layer 4b to the materials of compositions shown in the columns of ComparativeExample 1 to 7 in Table 1 above. The results of the evaluation of thesemagnetic recording media are shown in Table 1.

COMPARATIVE EXAMPLE 8

A film-forming chamber of a DC magnetron sputtering device (made byANELVA Corp., JAPAN and sold under the product code of “C-3010”)admitted a washed glass substrate (2.5 inches in outer length, productof Ohara K.K., JAPAN), and was evacuated till the degree of vacuumreached 1×10⁻⁵ Pa, and then operated to effect sputtering by using atarget of Co4Zr7Nb {4 at % of Zr content, 7 at % of Nb content and thebalance of Co} at a substrate temperature of 100° C. or less to form asoft magnetic primary coat 2 of a thickness of 100 nm on the glasssubstrate. By a test with a vibration system magnetic property testingdevice (VSM), the product Bs·t (T·nm) of the saturated magnetic fluxdensity Bs (T) multiplied by the film thickness t (nm) of this film wasconfirmed to be 120 (T·nm).

On the soft magnetic primary coat 2 mentioned above, a Ni40Ta {40 at %of Ta content and the balance of Ni} target and a Ru target weresequentially deposited in a thickness of 5 nm and 20 nm, respectively,to give rise to an orientation-controlling layer 3.

On the orientation-controlling layer 3, a target formed of(Co14Cr18Pt)90-(SiO₂)10 {90 mol % of an alloy composition comprising 14at % of Cr content, 18 at % of Pt content and the balance of Co and 10mol % of an oxide consisting of SiO₂} was deposited by sputtering undera pressure of 8 Pa to form a magnetic layer 4 a in a thickness of 10 nm.

Then, as the magnetic layer 4 b, layers respectively of targets of Coand Pd were alternately superposed in a Co thickness of 0.2 nm and a Pdthickness of 0.5 nm to form a laminated [Co/Pd] film. The number oflayers thus laminated was 10. The sputtering pressure was 3 Pa.

Then, a protective layer 5 of a film thickness of 5 nm was formed by theCVD technique. Subsequently, a lubricating layer 6 of perfluoropolyetherwas formed by the dipping technique to complete a magnetic recordingmedium.

COMPARATIVE EXAMPLES 9 AND 10

Magnetic recording media were manufactured by following the procedure ofComparative Example 8 while changing the number of superposed films ofthe magnetic layer 4 b to 20. The results of the rating of the magneticrecording media of Comparative Examples 9 and 10 are shown in Table 1above.

EXAMPLES 21 TO 39

Magnetic recording media were manufactured by following the procedure ofExample 1 while changing the magnetic layer 4 a and the magnetic layer 4b to the compositions and the conditions shown in Table 2. The resultsof the rating of the magnetic recording media of Examples 21 to 39 areshown in Table 2.

TABLE 2 Magnetic layer 4 Magnetic properties Magnetic layer 4a Magneticlayer 4b Static magnetic Film- Film- property Read/write Property ofthermal Composition Thick- forming Composition Thick- forming Coerciveproperty fluctuation {(at %)mol %} ness pressure (at %) ness pressureforce -Hn Ow S/N (% decade) Ex.21 {(Co12Cr16Pt)93- 10 (nm) 8 (Pa)(Co12Cr16Pt) 10 (nm) 3 (Pa) 3300(Oe) 1800(Oe) 51.5 19.3 0.11 (SiO₂)7}(dB) (dB) Ex.22 Same as above 10 8 (Co14Cr16Pt) 10 3 3700 1800 50.0 19.70.11 Ex.23 Same as above 10 8 (Co19Cr16Pt) 10 3 4000 1800 49.0 20.8 0.12Ex.24 Same as above 10 8 (Co26Cr16Pt) 10 3 4600 1700 50.5 20.1 0.14Ex.25 Same as above 10 8 (Co28Cr16Pt) 10 3 4550 1100 51.0 18.5 0.19Ex.26 {(Co10Cr15Pt- 10 8 (Co19Cr8Pt) 10 3 3400 1300 53.0 18.9 0.232Cu)92-(SiO₂)8} Ex.27 Same as above 10 8 (Co19Cr10Pt) 10 3 3550 140052.0 19.2 0.20 Ex.28 Same as above 10 8 (Co19Cr16Pt) 10 3 4150 1750 48.521.1 0.11 Ex.29 Same as above 10 8 (Co19Cr20Pt) 10 3 4600 1900 45.5 20.80.10 Ex.30 Same as above 10 8 (Co19Cr24Pt) 10 3 4300 1750 48.0 20.1 0.10Ex.31 {(Co10Cr14Pt- 10 8 (Co19Cr16Pt) 10 3 3950 1750 49.0 20.9 0.104Mo)92-(SiO₂)8} Ex.32 {(Co10Cr14Pt- 10 8 Same as 10 3 4050 1850 48.520.4 0.10 4Nb)92-(SiO₂)8} above Ex.33 {(Co10Cr14Pt- 10 8 (Co19Cr16Pt- 103 4100 1900 51.0 21.6 0.08 3Ta)92-(SiO₂)8} 2Nd) Ex.34{(Co10Cr14Pt4Ta-6W)92- 10 8 (Co19Cr16Pt- 10 3 3500 1200 54.0 19.4 0.20(Cr₂O₃)8} 3B) Ex.35 {(Co10Cr14Pt4Ta- 10 8 Same as 10 3 3950 1650 52.019.9 0.16 4W)92--(Cr₂O₃)8} above Ex.36 {(Co10Cr14Pt2Ru)94- 15 6(Co16Cr18Pt- 10 3 3750 1600 51.0 19.1 0.17 (Ta₂O₅)6} 4Re2Tb) Ex.37{(Co10Cr14Pt)90- 6 3 (Co19Cr16Pt- 24 0.7 3950 1800 49.0 19.3 0.15(TiO₂)10} 2B2Cu) Ex.38 {(Co10Cr14Pt)90- 25 15 (Co19Cr16Pt- 15 2 38501600 54.0 18.7 0.22 (SiO₂)4-(Al₂O₃)6} 2Ta2Nd) Ex.39 {(Co10Cr18Pt5Cu)88-18 12 (Co23Cr16Pt- 12 7 4100 1650 52.0 19.3 0.16 (MgO)8-(Y₂O₃)4} 1Cu-1B)

EXAMPLES 40 AND 41

Magnetic recording media were manufactured by following the procedure ofExample 1 while changing the construction of the perpendicularlymagnetic layer 4 to the sequence of film formation (magnetic layer 4 band magnetic layer 4 a). The results of the rating of the magneticrecording media of Examples 40 and 41 are shown in Table 3.

TABLE 3 Example 40 Example 41 Magnetic Magnetic layer 4b layer 4Composition (at %) (Co12Cr16Pt) (Co20Cr12Pt3Sm) Thickness (nm) 10 6Film-forming Pressure (Pa) 2 0.7 Magnetic layer 4a Composition {(at%)mol %} {(Co12Cr16Pt)93—(SiO₂)7} {(Co10Cr14Pt)94—(SiO₂)6} Thickness(nm) 10 16 Film-forming Pressure (Pa) 6 4 Magnetic Static magneticproperty properties Coercive force (Oe) 3650 3700 -Hn (Oe) 1550 1650Read/write property OW (dB) 53 52.0 S/N (dB) 18.5 18.6 Property ofthermal 0.12 0.12 fluctuation (% decade)

EXAMPLES 42 TO 44

Magnetic recording media were manufactured by following the procedure ofExample 1 while changing the construction of the perpendicularlymagnetic layer 4 to the sequence of film formation (magnetic layer 4 a,magnetic layer 4 b-1 and magnetic layer 4 b-2) shown in Table 4 andchanging the compositions thereof to those shown in Table 4. The resultsof the rating of the magnetic recording media of Examples 42 to 44 areshown in Table 4.

TABLE 4 Example 42 Example 43 Example 44 Magnetic Magnetic layer 4 layer4a Composition {(Co8Cr12Pt)94—(SiO₂)6} {(Co8Cr12Pt)94—(SiO₂)6}{(Co10Cr—16Pt)94—(Cr₂O₃)6} {(at %)mol %} Thickness 14 (nm)  14 12 Film-5 5 9 forming pressure Magnetic layer 4b-1 Composition (Co23Cr14Pt)(Co23Cr14Pt) (Co16Cr12Pt2B) (at %) Thickness 6 (nm) 6 7 Film- 0.7 (Pa)0.7 3 forming pressure Magnetic layer 4b-2 Composition (Co18Cr12Pt2Nd)(Co14Cr18Pt2Cu) (Co22Cr16Pt1W) (at %) Thickness 4 (nm) 6 8 Film-   3(Pa) 2 0.7 forming pressure Magnetic Static properties magnetic propertyCoercive 4000 4150 4200 force (Oe) -Hn (Oe) 1900 1750 1850 Read/writeproperty OW (dB) 49 53 51 S/N (dB) 20.9 21.1 21.2 Property of 0.11 0.120.11 thermal fluctuation (% decade)

EXAMPLES 46 AND 47

Magnetic recording media were manufactured by following the procedure ofExample 1 while changing the construction of the perpendicularlymagnetic layer 4 to the sequence of film formation (magnetic layer 4b-1, magnetic layer 4 a-1, magnetic layer 4 b-2, magnetic layer 4 a-2and magnetic layer 4 b-3) shown in Table 5 and also changing thecompositions to those shown in Table 5. The results of the rating of themagnetic recording media of Examples 46 and 47 are shown in Table 5.

TABLE 5 Example 46 Example 47 Magnetic Magnetic layer 4b-1 layer 4Composition (at %) (Co20Cr14Pt2B) (Co20Cr14Pt2B) Thickness (nm) 4 4Film-forming pressure (Pa) 0.7 0.7 Magnetic layer 4a-1 Composition {(at%)mol %} {(Co14Cr18Pt)95—(SiO₂)5} {(Co14Cr14Pt)95—(SiO₂)5} Thickness(nm) 4 4 Film-forming pressure (Pa) 6 6 Magnetic layer 4b-2 Composition(at %) (Co20Cr14Pt12B) (Co14Cr16Pt2Cu) Thickness (nm) 4 0.7 Film-formingpressure (Pa) 6 2 Magnetic layer 4a-2 Composition {(at %)mol %}{(Co14Cr18Pt)95—(SiO₂)5} {(Co14Cr18Pt)95—(Cr₂O₃)5} Thickness 4 6Film-forming pressure 6 3 Magnetic layer 4b-3 Composition (at %)(Co20Cr14Pt2B) (Co20Cr14Pt2B) Thickness (nm) 4 4 Film-forming pressure(Pa) 0.7 0.7

TABLE 6 Magnetic properties Static magnetic Read/write Property ofproperty property thermal Coercive force Ow fluctuation (Oe) −Hn (Oe)(dB) S/N (dB) (% decade) Ex. 46 3950 1550 49.0 22.5 0.11 Ex. 47 41501600 49.0 22.7 0.10

EXAMPLE 48

A magnetic recording medium was manufactured by following the procedureof Example 1 while changing the construction of the perpendicularlymagnetic layer 4 to the sequence of film formation (magnetic layer 4 a,magnetic layer 4 b-1, nonmagnetic layer 9, magnetic layer 4 b-2) shownin Table 6 and also changing the composition to that of Table 7. Theresults of the rating of the magnetic recording medium of Example 48 areshown in Table 7.

TABLE 7 Example 48 Magnetic Magnetic layer 4a layer 4 Composition{(Co12Cr17Pt1W)95—(Al₂O₃)5} {(at %)mol %} Thickness (nm) 10 Film-formingpressure 6 (Pa) Magnetic layer 4b-1 Composition (at %) (Co24Cr16Pt)Thickness (nm) 5 Film-forming pressure 3 (Pa) Nonmagnetic layer 9Composition (at %) (Co35Cr) Thickness (nm) 2 Magnetic layer 4b-2Composition (at %) (Co19Cr12Pt13Re) Thickness (nm) 6 Film-formingpressure 2 (Pa) Magnetic Static magnetic property properties Coerciveforce (Oe) 3850 -Hn (Oe) 1700 Read/wire property Ow (dB) 48 S/N (dB)22.9 Property of 0.13 thermal fluctuation (% decade)

EXAMPLE 49

A magnetic recording medium was manufactured by following the procedureof Example 1 while changing the construction of the perpendicularlymagnetic layer 4 to the sequence of film formation (magnetic layer 4a-1, nonmagnetic layer 9, magnetic layer 4 a-2 and magnetic layer 4 b)shown in Table 8 and also changing the composition to that shown inTable 8. The results of the rating of the magnetic recording medium ofExample 49 are shown in Table 8.

TABLE 8 Example 49 Magnetic Magnetic layer 4a-1 layer 4 Composition{(Co10Cr11Pt1W)92—(MgO)8} {(at %)mol %} Thickness (nm) 12 Film-formingpressure (Pa) 4 Nonmagnetic layer 9 Composition (at %) Ru Thickness (nm)1 Magnetic layer 4a-2 Composition (at %) (Co25Cr14Pt4B) Thickness (nm) 4Film-forming pressure (Pa) 3 Magnetic layer 4b Composition (at %)(Co19Cr11Pt3B) Thickness (nm) 4 Film-forming pressure (Pa) 3 MagneticStatic magnetic property properties Coercive force (Oe) 3750 -Hn (Oe)1600 Read/write property Ow (dB) 49 S/N (dB) 21.5 Property of 0.11thermal fluctuation (% decade)

EXAMPLES 50 TO 53

Magnetic recording media were manufactured by following the procedure ofExample 1 while changing the construction of the perpendicularlymagnetic layer 4 to the sequence of film formation (magnetic layer 4a-1, nonmagnetic layer 9, magnetic layer 4 a-2 and magnetic layer 4 b)shown in Table 9 and also changing the compositions to those shown inTable 9. The results of the rating of the magnetic recording media ofExamples 50 to 53 are shown in Table 9.

TABLE 9 Example 50 Example 51 Magnetic Magnetic layer 4a-1 layer 4Composition {(at %)mol %} {(Co12Cr15Pt)90- {(Co12Cr15Pt)90- (Y₂O₃)10}(Y₂O₃)10} Thickness (nm) 8 8 Film-forming pressure (Pa) 5 5 Nonmagneticlayer 9 Composition {(at %)mol %} {(Co50CRu)93- {(Co50Ru)93- (SiO₂)7}(TiN)7} Thickness (nm) 2 1.5 Magnetic layer 4a-2 Composition {(at %)mol%} {(Co12Cr11Pt)90- (Co12Cr11Pt)90- (Y₂O₃)10} (Y₂O₃)10} Thickness (nm) 88 Film-forming pressure (Pa) 8 8 Magnetic layer 4b Composition (at %)(Co19Cr11Pt3B) (Co19Cr11Pt3B) Thickness (nm) 4 4 Film-forming pressure(Pa) 3 3 Example 52 Example 53 Magnetic Magnetic layer 4a-1 layer 4Composition {(at %)mol %} {(Co12Cr15Pt)90- {(Co12Cr15Pt)90- (Y₂O₃)10}(Y₂O₃)10} Thickness (nm) 8 8 Film-forming pressure (Pa) 5 5 Nonmagneticlayer 9 Composition {(at %)mol %} {(Co50CRu)93- {(Co50Ru)93- (SiO₂)7}(TiN)7} Thickness (nm) 2 1.5 Magnetic layer 4a-2 Composition {(at %)mol%} {(Co12Cr11Pt)90- (Co12Cr11Pt)90- (Y₂O₃)10} (Y₂O₃)10} Thickness (nm) 88 Film-forming pressure (Pa) 8 8 Magnetic layer 4b Composition (at %)(Co19Cr11Pt3B) (Co19Cr11Pt3B) Thickness (nm) 4 4 Film-forming pressure(Pa) 3 3 Magnetic properties Static magnetic property Read/writeProperty of thermal Coercive force property fluctuation (Oe) -Hn (Oe) Ow(dB) S/N (dB) (% decade) Ex. 50 3900 1700 50 21.1 0.13 Ex. 51 3800 165050 21.5 0.13 Ex. 52 3950 1700 51 20.8 0.13 Ex. 53 3400 1450 53 19.4 0.15

EXAMPLE 54

A film-forming chamber of a DC magnetron sputtering device (made byANELVA Corp., JAPAN and sold under the product code of “C-3010”)admitted a washed glass substrate (2.5 inches in outer length, productof Ohara K.K., JAPAN), and was evacuated till the degree of vacuumreached 1×10⁻⁵ Pa, and then operated to effect sputtering by using atarget of Co4Zr7Nb {4 at % of Zr content, 7 at % of Nb content and thebalance of Co} at a substrate temperature of 100° C. or less to form asoft magnetic primary coat 2 of a thickness of 100 nm on the glasssubstrate. By a test with a vibration system magnetic property testingdevice (VSM), the product, Bs·t (T·nm) of the saturated magnetic fluxdensity Bs (T) multiplied by the film thickness t (nm) of this film wasconfirmed to be 120 (T·nm).

On the soft magnetic primary coat 2, a film was formed in a thickness of20 nm by using a Ru target to give rise to an orientation-controllinglayer.

On the orientation-controlling layer 3, a (Co12Cr20Pt)90-(SiO₂)10 {90mol % of an alloy composition comprising 12 at % of Cr content, 20 at %of Pt content and the balance of Co and 10 mol % of an oxide consistingof SiO₂} target was deposited in a thickness of 10 nm under a sputteringpressure of 0.7 Pa to give rise to a magnetic layer 4 a.

Then, a target formed of Co20Cr13Pt3B {20 at % of Cr content, 13 at % ofPt content, 3 at % of B content and the balance of Co} was depositedunder a sputtering pressure of 3 Pa to give rise to a magnetic layer 4 bin a thickness of 10 nm.

Subsequently, a protective layer 5 of a thickness of 5 nm was formed bythe CVD technique. Then, a lubricating layer 6 of perfluoropolyether wasformed by the dipping technique to complete a magnetic recording medium.The results of the rating of the magnetic recording medium of Example 54are shown in Table 10.

TABLE 10 Magnetic properties Static magnetic Read/write PropertyOrientation-controlling layer 3 Intermediate layer 8 property propertyof thermal Composition Thickness Composition Thickness Coercive force Owfluctuation {(at %)mol %} (nm) {(at %)mol %} (nm) (Oe) -Hn (Oe) (dB) S/N(dB) (% decade) Ex. 54 Ru 20 — — 4200 1600 50 20.9 0.13 Ex. 55 Pd 15 — —4300 1550 51 20.5 0.14 Ex. 56 Pt 15 — — 4500 1800 49 21.5 0.11 Ex. 57{(Ru)90-(SiO₂)10} 25 — — 3600 1400 54 20.8 0.15 Ex. 58{(Ni40Ta)95-(TiO₂)5} 25 — — 3400 1100 55 19.6 0.21 Ex. 59{(Pt)94-(TaC)6} 30 — — 3500 1250 54 20.4 0.19 Ex. 60 {(Pt)94-(Si₃N₄)6}20 — — 3600 1100 54 19.4 0.17 Ex. 61 Ru 20 {Co35Cr} 2 4500 1750 50 21.50.11 Ex. 62 Ru 20 (C40Cr8pt3Ta) 3 4450 1800 49 21.8 0.11 Ex. 63 Ru 20{(Co30Cr5Pt)94-(Cr₂O₃)6} 5 3900 1550 50 21.1 0.14 Ex. 64 Ru 20{(Co38Cr4Pt6B)92-(AlN)8} 5 3800 1600 50 20.4 0.16 Ex. 65 Ru 20{(Co38Cr4Pt6B)92-(BC)8} 5 3400 1200 51 19.3 0.19 Ex. 66 Ru 20{Ca38Cr4Pt4B}92-(Al₂O₃)8} 8 3600 1350 51 19.5 0.17

EXAMPLES 55 TO 60

Magnetic recording media were manufactured by following the procedure ofExample 54 while changing the material of the orientation-controllinglayer to the materials shown in Table 10. The results of the rating ofthe magnetic recording media of Examples 55 to 60 are shown in Table 10.

EXAMPLE 61

A film-forming chamber of a DC magnetron sputter device (made by ANELVACorp., JAPAN and sold under the product code of “C-3010”) admitted awashed glass substrate (2.5 inches in outer length, product of OharaK.K., JAPAN), and was evacuated till the degree of vacuum reached 1×10⁻⁵Pa and then operated to effect sputtering by using a target of Co4Zr7Nb{4 at % of Zr content, 7 at % of Nb content and the balance of Co} at asubstrate temperature of 100° C. or less to form a soft magnetic primarycoat 2 of a thickness of 100 nm on the glass substrate. By a test with avibration system magnetic-property testing device (VSM), the productBs·t (T·nm) of the saturated magnetic flux density Bs (T) multiplied bythe film thickness t (nm) of this film was confirmed to be 120 (T·nm).

On the soft magnetic primary coat 2 mentioned above, a film was formedin a thickness of 20 nm by using a Ru target to give rise to anorientation-controlling layer 3.

On the orientation-controlling layer 3, a film was formed in a thicknessof 2 nm by using a Co35Cr {35 at % of Cr content and the balance of Co}target to give rise to an intermediate layer 8.

On the intermediate layer 8, a magnetic layer 4 a was formed in athickness of 10 nm by using a (Co12Cr20Pt)90-(SiO₂)10 {90 mol % of analloy composition comprising 12 at % of Cr content, 20 at % of Ptcontent and the balance of Co and 10 mol % of an oxide consisting ofSiO₂} target under a sputtering pressure of 0.7 Pa.

Subsequently, a magnetic layer 4 b was formed in a thickness of 10 nm byusing a target formed of Co20Cr13Pt3B {20 at % of Cr content, 13 at % ofPt content, 3 at % of B content and the balance of Co} under asputtering pressure of 3 Pa.

Subsequently, a protective layer 5 was formed in a thickness of 5 nm bythe CVD technique. Then, a lubricating layer 6 of perfluoropolyether wasformed by the dipping technique to complete a magnetic recording medium.The results of the rating of the magnetic recording medium of Example 61are shown in Table 10.

EXAMPLES 62 TO 66

Magnetic recording media were manufactured by following the procedure ofExample 61 while changing the material to the materials shown in Table10. The results of the rating of the magnetic recording media of Example62 to 66 are shown in Table 10.

EXAMPLES 67 TO 78

Magnetic recording media were manufactured by following the procedure ofExample 1 while changing the conditions of the perpendicularly magneticlayer 4, such as the material, added gas and substrate bias, to theconditions shown in Table 11. The results of the rating of the magneticrecording media of Examples 67 to 78 are shown in Table 11.

TABLE 11 Magnetic layer 4 Magnetic layer 4a Composition ThicknessFilm-forming {(at %)mol %} (nm) pressure (Pa) Added gas Substrate biasEx. 67 {(Co10Cr16tPt)92- 9 6 — — SiO₂)8} Ex. 68 Same as above 9 6 O₂ -0.3 vol % — Ex. 69 Same as above 9 6 O₂ - 0.6 vol % — Ex. 70 Same asabove 9 6 O₂ - 1.2 vol % — Ex. 71 Same as above 9 6 O₂ - 2 vol % — Ex.72 Same as above 9 6 O₂ - 4 vol % — Ex. 73 Same as above 9 6 N₂ - 0.5vol % — Ex. 74 Same as above 9 6 O₂ - 0.6 vol % — Ex. 75 Same as above 96 O₂ - 0.6 vol % −150 V Ex. 76 Same as above 9 6 O₂ - 0.6 vol % −300 VEx. 77 Same as above 9 6 O₂ - 0.6 vol % −600 V Ex. 78 Same as above 9 6O₂ - 0.6 vol % — Magnetic layer 4 Magnetic layer 4b CompositionThickness Film-forming (at %) (nm) pressure (Pa) Added gas Substratebias Ex. 67 (Co23Cr16Pt1Cu1B) 9 0.7 — — Ex. 68 Same as above 9 0.7 — —Ex. 69 Same as above 9 0.7 — — Ex. 70 Same as above 9 0.7 — — Ex. 71Same as above 9 0.7 — — Ex. 72 Same as above 9 0.7 — — Ex. 73 Same asabove 9 0.7 — — Ex. 74 Same as above 9 0.7 O₂ - 0.3 vol % — Ex. 75 Sameas above 9 0.7 — — Ex. 76 Same as above 9 0.7 — — Ex. 77 Same as above 90.7 — — Ex. 78 Same as above 9 0.7 — −200 V Magnetic properties Staticmagnetic property Read/write Property of thermal Coercive force propertyfluctuation (Oe) -Hn (Oe) Ow (dB) S/N dB (% decade) Ex. 67 4300 200051.5 21.5 0.09 Ex. 68 4450 2000 50.5 21.9 0.09 Ex. 69 4600 2000 49 22.50.09 Ex. 70 4550 2000 49 22.4 0.09 Ex. 71 4500 1950 50 22.1 0.09 Ex. 724200 1600 53 19.7 0.13 Ex. 73 4300 1850 52 21.8 0.09 Ex. 74 4400 190051.5 22.9 0.09 Ex. 75 4700 2050 49 22.6 0.09 Ex. 76 4700 2000 49 22.80.09 Ex. 77 4650 2000 49 22.5 0.09 Ex. 78 4750 2000 48 23.5 0.09

It is revealed from the comparison of Example 5 with ComparativeExamples 1, 2, 4, 5, 6, 8, 9 and 10 in Table 1 that in the formation ofthe perpendicularly magnetic layer 4 contemplated by this invention, theconstruction of this perpendicularly magnetic layer 4 with a magneticfilm having Co as a main component, containing Pt as well and containingan oxide and a magnetic layer having Co as a main component, containingCr as well and containing no oxide manifests an effect peculiar thereto.It is noted that Example 5 of this invention enhanced the nucleation(−Hn) to a great extent and manifested the property of thermalfluctuation and the read/write property (S/N ratio and recordingproperty) favorably as compared with Comparative Examples 1 and 2 whichformed only oxide-containing magnetic layers.

It is learnt from the comparison of Example 5 with Comparative Examples6, 7, 8 and 9 that for this invention, the fact that the magnetic layer4 b has Co as a main component and contains at least Cr is important.

It is learnt from the comparison of Example 1 with Comparative Example 3that the formation of a perpendicularly magnetic layer 4 necessitates amagnetic layer having at least one layer containing an oxide.

It is learnt from the comparison of Examples 5 and 9 to 13 that thecontent of the oxide in the oxide-containing magnetic layer 4 a ispreferred to be 3 mol % or more and 12 mol % or less

It is learnt from the comparison of Example 5 and 14 to 17 that the Crcontent in the oxide-containing magnetic layer 4 a is preferred to be 6at % or more and 16 at % or less.

It is learnt from the comparison of Examples 5 and 18 to 20 the Ptcontent in the oxide-containing magnetic layer 4 a is preferred to be 10at % or more and 20 at % or less.

Then in Table 2, it is learnt from the comparison of Examples 21 to 25that the Cr content in the magnetic layer 4 b containing no oxide ispreferred to be 14 at % or more and 30 at % or less.

It is learnt from the comparison of Examples 26 to 30 that the Ptcontent in the magnetic layer 4 b containing no oxide is preferred to 8at % or more and 20 at % or less.

It is learnt from Table 2 that the oxide of the oxide-containingmagnetic layer 4 a is preferred to be Cr₂O₃, SiO₂ or Ta₂O₅. It isfurther learnt that it may be a material containing a plurality ofoxides.

It is learnt that the material to be used for the perpendicularlymagnetic layer 4 may contain at least one element selected from thegroup consisting of B, Ta, Mo, Cu, Nd, W, Nb, Sm, Th, Ru and Re besidesCo, Cr and Pt.

It is learnt from Table 3 that the construction of the perpendicularlymagnetic layer 4 may be such that the magnetic layer 4 b containing nooxide and the oxide-containing magnetic layer 4 a are sequentiallyplaced in the order mentioned.

It is learnt from Table 4, Table 5 and Table 6 that the perpendicularlymagnetic layer 4 may be constructed of three kinds of magnetic layers.

It is learnt from Table 7, Table 8 and Table 9 that the nonmagneticlayer 9 may be formed between any of the adjacent component layers ofthe perpendicularly magnetic layer 4.

It is further learnt that the perpendicularly magnetic layer 4 may beconstructed of a plurality of oxide-containing magnetic layers.

It is learnt from Table 10 that the orientation-controlling layer 3 mayuse a material containing an oxide, metal nitride and metal carbidebesides a metallic material assuming the hcp structure of Ru, Pt or Pd.

It is further learnt that the intermediate layer 8 may be interposedbetween the orientation-controlling layer 3 and the perpendicularlymagnetic layer 4.

It is learnt from Table 11 that the addition of a gas during theformation of the perpendicularly magnetic layer 4 and the substrate biasresult in enhancing properties.

INDUSTRIAL APPLICABILITY

The magnetic recording medium of this invention, as described above, isprovided on a nonmagnetic substrate with at least anorientation-controlling layer for controlling the orientation of a layerformed directly thereon, a perpendicularly magnetic layer having aneasily magnetizing axis oriented mainly perpendicularly relative to thenonmagnetic substrate, and a protective layer and characterized in thatthe perpendicularly magnetic layer comprises two or more magneticlayers, at least one of the magnetic layers being a layer having Co as amain component and containing Pt as well and containing an oxide and atleast another of the magnetic layers being a layer having Co as a maincomponent and containing Cr as well and containing no oxide. By thisconfiguration, it is made possible to promote fine division and magneticisolation of the magnetic grains, enhance the signal/noise (S/N) ratioto a great extent during the course of reproduction, improve thenucleation (−Hn) and consequently exalt the property of thermalfluctuation and acquire a medium possessing a proper recording property(OW).

1. A magnetic recording medium comprising: a nonmagnetic substrate; andat least three layers formed on the nonmagnetic substrate and comprisedof a non-magnetic orientation-controlling layer for controllingorientation of a layer formed directly thereon, a perpendicular magneticlayer having an easily magnetizing axis oriented mainly perpendicularlyrelative to the nonmagnetic substrate, and a protective layer; saidperpendicular magnetic layer comprising two or more magnetic layers, atleast one of said magnetic layers being a lower layer having Co as amain component and containing Pt and an oxide and at least another ofsaid magnetic layers being an upper layer having Co as a main componentand containing Cr and no oxide; said lower magnetic layer being directlyadjacent and in contact with the orientation-controlling layer andcomprising magnetic crystal grains isolated by the oxide and dispersedin the lower layer and said crystal grains vertically penetrating saidlower layer in columnar forms; and said upper layer comprising magneticcrystal grains that are formed and epitaxially grown on the magneticcrystal grains of the lower layer in a ratio of one to one on an uppersurface of said lower layer.
 2. A magnetic recording medium according toclaim 1, wherein said oxide is an oxide of at least one nonmagneticmetal selected from among Cr, Si, Ta, Al and Ti.
 3. A magnetic recordingmedium according to claim 1, wherein said oxide is Cr₂O₃ or SiO₂.
 4. Amagnetic recording medium according to claim 1, wherein said magneticlayer containing the oxide has an oxide content of 3 mol % or more and12 mol % or less.
 5. A magnetic recording medium according to claim 1,wherein said magnetic layer containing the oxide has Co as a maincomponent and has a Cr content of 0 at % or more and 16 at % or less anda Pt content of 10 at % or more and 25 at % or less.
 6. A magneticrecording medium according to claim 1, wherein said magnetic layercontaining the oxide contains at least one element selected from thegroup consisting of B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru and Re and hasa total content of said at least one element that is 8 at % or less. 7.A magnetic recording medium according to claim 1, wherein said magneticlayer containing no oxide has Co as a main component and has a Crcontent of 14 at % or more and 30 at % or less.
 8. A magnetic recordingmedium according to claim 1, wherein the magnetic layer containing nooxide has Co as a main component and has a Cr content of 14 at % or moreand 30 at % or less and a Pt content of 8 at % or more and 20 at % orless.
 9. A magnetic recording medium according to claim 1, wherein saidmagnetic layer containing no oxide contains at least one elementselected from the group consisting of B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb,Ru and Re and has a total content of said at least one clement that is 8at % or less.
 10. A magnetic recording medium according to claim 1,wherein said perpendicular magnetic layer contains two or moreoxide-containing layers.
 11. A magnetic recording medium according toclaim 1, wherein said perpendicular magnetic layer contains two or morelayers containing no oxide.
 12. A method for the production of amagnetic recording medium comprising a nonmagnetic substrate and atleast three layers formed on the nonmagnetic substrate and comprised ofa non-magnetic orientation-controlling layer for controlling orientationof a layer formed directly thereon, a perpendicular magnetic layerhaving an easily magnetizing axis oriented mainly perpendicularlyrelative to the nonmagnetic substrate, and a protective layer, saidmethod comprising; forming said perpendicular magnetic layer of two ormore magnetic layers, wherein at least one of said two or more magneticlayers is a lower layer having Co as a main component, and containing Ptand an oxide and at least another of said two or more magnetic layers isan upper layer having Co as a main component, and containing Cr and nooxide; forming said lower layer directly adjacent and in contact withthe orientation-controlling layer and with magnetic crystal grainsisolated by the oxide and dispersed in the lower layer and verticallypenetrating the lower layer in columnar forms; and forming said upperlayer by forming and epitaxially growing magnetic crystal grains on themagnetic crystal grains of the lower layer in a ratio of one to one onan upper surface of the lower layer.
 13. A method according to claim 12,wherein said perpendicular magnetic layer contains two or moreoxide-containing layers.
 14. A method according to claim 12, whereinsaid perpendicular magnetic layer contains two or more layers containingno oxide.
 15. A method according to claim 12, wherein said perpendicularmagnetic layer is formed using a film-forming gas to which an oxygen gasis added.
 16. A magnetic recording and reproducing apparatus furnishedwith a magnetic recording medium and a magnetic head for recording andreproducing information in said magnetic recording medium, saidapparatus being characterized in that said magnetic recording medium isthe magnetic recording medium set forth in claim 1.